i  -fifth 


mmim 


,:* 


Sheffield  Laboratory  of  Yale  University 


PAPERS  ON  PYRIMIDINES 

EDITED  BY 

HENRY  L.  WHEELER 

o 

PROFESSOR  OF  ORGANIC  CHEMISTRY 

AND 

TREAT  B.  JOHNSON 

ASSISTANT  PROFESSOR  OF  ORGANIC  CHEMISTRY. 


NEW  HAVEN,  CONNECTICUT, 
U.  S.  A. 


PREFACE 


In  the  present  volume  the  Authors  have  incorporated  all  the 
Papers  on  Pyrimidines,  which  have  appeared  from  the  Sheffield 
Laboratory  prior  to  the  year  1910. 

A  bibliography  of  publications  on  pyrimidines,  arranged 
chronologically,  has  also  been  appended  to  this  book,  but  it 
must  be  understood  that  it  is  not  intended  to  be  complete.  The 
aim  of  the  authors  has  been  to  furnish  a  guide  to  readers,  who 
are  unacquainted  with  pyrimidine  literature,  rather  than  to 
give  a  complete  list  of  publications  in  this  field. 

H.  L.  W.  and  T.  B.  J. 

Sheffield  Laboratory,  New  Haven. 
January,  1910. 


^58663 


CONTENTS 

RESEARCHES  ON  THE  CYCLOAMIDINES  :  PYRIMIDINE  DERIVA- 
TIVES. By  Henry  L.  Wheeler.  (American  Chemical 
Journal,  1898,  XX,  481). 

ON  SOME  CONDENSATION-PRODUCTS  OF  THE  PSEUDOTHIOUREAS  : 
SYNTHESIS  OF  URACIL,  THYMINE  AND  SIMILAR  COM- 
POUNDS. By  Henry  L.  Wheeler  and  Henry  F.  Merriam. 
(American  Chemical  Journal,  1903,  XXIX,  478). 

SYNTHESES  OF  AMINOOXYPRIMIDINES  HAVING  THE  COMPOSI- 
TION OF  CYTOSINE:  2-AMiNO-6-OxYPYRiMmiNE  AND 
2-OxY-6-AMiNOPYRiMiDiNE.  By  Henry  L.  Wheeler 
and  Treat  B.  Johnson.  (American  Chemical  Journal, 

1903,  XXIX,  492). 

ON  CYTOSINE  OR  2-OxY-6-AMiNOPYRiMiDiNE  FROM  TRITICO- 

NUCLEIC  ACID.     By  Henry  L.  Wheeler  and  Treat  B. 

Johnson.     (American  Chemical  Journal,  1903,  XXIX, 

505). 
5-METHYLCYTOSiNE.     By   Henry  L.   Wheeler   and   Treat   B.  ^ 

Johnson.     (American  Chemical  Journal,  1904,  XXXI, 

591). 
SYNTHESIS    OF   2-AMiNO-5-METHYL-6-OxYPYRiMiDiNE.       By 

Treat  B.  Johnson  and  Samuel  H.  Clapp.     (American 

Chemical  Journal,  1904,  XXXII,  130). 
2-OxY-4,  6-DiAMiNOPYRiMiDiNE.     By  Henry  L.  Wheeler  and 

George  S.   lamieson.      (American    Chemical    Journal, 

1904,  XXXII,  342). 

THE  STRUCTURE  OF  SOME  SUBSTITUTION  PRODUCTS.  By 
Henry  L.  W'heeler  and  H.  Stanley  Bristol.  (American 
Chemical  Journal,  1905,  XXXIII,  437). 

THE  ACTION  OF  POTASSIUM  THIOCYANATE  UPON  SOME  IMIDE- 
CHLORIDES.  By  Henry  L.  Wheeler  and  H.  Stanley 
Bristol.  (American  Chemical  Journal,  1905,  XXXIII, 
448). 

THE  ACTION  OF  AQUEOUS  AND  ALCOHOLIC  AMMONIA  AND 
ANILINE  ON  SOME  HALOGEN  AND  MERCAPTO  PYRIMI- 
DINES.  By  Treat  B.  Johnson  and  Carl  O.  Johns. 
(American  Chemical  Journal,  1905,  XXXIV,  175). 


^s>W       CONTENTS 

2-ETHYLMERCAPTO-5-AMiNO-6-OxYPYRiMiDiNE.  By  Treat  B. 
Johnson.  (American  Chemical  Journal,  1905  XXXIV, 
191). 

ON  2,  5-DiAMiNO-6-OxYPYRiMiDiNE.  By  Treat  B.  Johnson 
and  Carl  O.  Johns.  (American  Chemical  Journal,  1905, 
XXXIV,  554). 

SOME  5-IoDOPYRiMiDiN  DERIVATIVES:  S-IODOCYTOSINE.  By 
Treat  B.  Johnson  and  Carl  O.  Johns.  (Journal  of 
Biological  Chemistry,  1906,  I,  305). 

ON  METHODS  OF  SYNTHESIZING  ISOBARBITURIC  ACID  AND  5- 
OXYCYTOSIN.  By  Treat  B.  Johnson  and  Elmer  V. 
McCollum.  (Journal  of  Biological  Chemistry,  1906,  I, 
437). 

THE  ACTION  OF  POTASSIUM  THIOCYANATE  UPON  IMIDE 
CHLORIDES.  By  Treat  B.  Johnson  and  Elmer  V.  Mc- 
Collum. (American  Chemical  Journal,  1906,  XXXVI, 
136). 

ON  THE  FORMATION  OF  PURINES  FROM  UREAPYRIMIDINES.  By 
Treat  B.  Johnson  and  Elmer  V.  McCollum.  (Ameri- 
can Chemical  Journal,  1906,  XXXVI,  149). 

ON     5-NlTROCYTOSINE    AND    ITS    REDUCTION    TO    2-OXY-5,    6- 

DIAMINOPYRIMIDINE.  By  Treat  B.  Johnson,  Carl  O. 
Johns  and  Frederick  W.  Heyl.  (American  Chemical 
Journal,  1906,  XXXVI,  160). 

5-ETHYLCYTOSiN.  By  Treat  B.  Johnson  and  George  A. 
Menge.  (Journal  of  Biological  Chemistry,  1906,  II, 
105). 

SYNTHESIS  OF  URACIL-S-CARBOXYLIC  ACID.  By  Henry  L. 
Wheeler,  Treat  B.  Johnson  and  Carl  O.  Johns.  (Ameri- 
can Chemical  Journal,  1907,  XXXVII,  392. 

ON  A  COLOR  TEST  FOR  URACIL  AND  CYTOSIN.  By  Henry  L. 
Wheeler  and  Treat  B.  Johnson.  (Journal  of  Biologi- 
cal Chemistry,  1907,  III,  183). 

ON  SOME  SALTS  OF  CYTOSIN,  ISOCYTOSIN,  6-AMiNOPYRiMioiN 
AND  6-OxYpYRiMiDiN.  By  Henry  L.  Wheeler.  (Jour- 
nal of  Biological  Chemistry,  1907,  III,  285). 

URACiL-4-CARBOXYLic  ACID.  By  Henry  L.  Wheeler.  (Ameri- 
can Chemical  Journal,  1907,  XXXVIII,  358). 

THE  ACTION  OF  METHYL  IODIDE  ON  2-ANiLiNO-6-OxYpRiMi- 

DINE,    AND    THE    SYNTHESIS    OF    2-ANILINOPYRIMIDINE. 

By  Treat  B.  Johnson  and  Frederick  W.  Heyl.  (Ameri- 
can Chemical  Journal,  1907,  XXXVIII.  237). 


CONTENTS  7 

SYNTHESIS  OF  THYMiN-4-CARBOXYLic  ACID  ^   By   Treat   B. 

Johnson.     (Journal  of  Biological  Chemistry,  1907,  111. 

299). 
SYNTHESIS  OF  CYTOSINE-S-CARBOXYLIC  ACID.     By  Henry  L. 

Wheeler    and    Carl    O.    Johns.      (American    Chemical 

Journal,  1907,  XXXVIII,  594). 
SYNTHESIS  OF  THYMINE-S-CARBOXYLIC  ACID.     By  Treat  B. 

Johnson  and  Carl  Frank  Speh.     (American  Chemical 

Journal,  1907,  XXXVIII,  602). 
SYNTHESIS  OF  4-METHYLURACiL-5-AcETic  ACID.    By  Treat  B. 

Johnson  and  Frederick  W.  Heyl.     (American  Chemical 

Journal,  1907,  XXXVIII,  659). 
A  METHOD  OF  SEPARATING  THYMIN  FROM  URACIL.    By  Treat 

B.  Johnson.     (Journal  of  Biological  Chemistry,  1908, 

IV,  407). 

THE  ACTION  OF  NITRIC  ACID  ON  2,  6-DioxYPYRiMmiNES.  OXY- 
NITROHYDROTHYMINE.  By  Treat  B.  Johnson.  (Ameri- 
can Chemical  Journal,  1908,  XL,  19). 

SYNTHESIS  OF  URAciL-3-AcETic  ACID.  By  Henry  L.  Wheeler 
and  Leonard  M.  Liddle.  (Journal  American  Chemical 
Society,  1908,  XXX,  1152). 

SYNTHESIS  OF  URACiL-4-AcETic  ACID.  By  Henry  L.  Wheeler 
and  Leonard  M.  Liddle.  (Journal  American  Chemical 
Society,  1908,  XXX,  1156). 

SYNTHESIS  OF  SOME  NITROGEN-ALKYL  DERIVATIVES  OP- 
CYTOSIN,  THYMIN  AND  URACIL.  By  Treat  B.  Johnson 
and  Samuel  H.  Clapp.  (Journal  of  Biological  Chemis- 
try, 1908,  V,  49). 

THE  ACTION  OF  DIAZO-BENZENE  SULFONIC  ACID  ON  THYMIN, 
URACIL  AND  CYTOSIN.  By  Treat  B.  Johnson  and  Sam- 
uel H.  Clapp.  (Journal  of  Biological  Chemistry,  1908, 

V,  163). 

THE  ACTION  OF  POTASSIUM  THIOCYANATE  UPON  SOME  IMIDE 
CHLORIDES.  By  Treat  B.  Johnson  and  Walter  F.  Storey. 
(American  Chemical  Journal,  1908,  XL,  131). 

SYNTHESIS  OF  CYTOSINE-S-CARBOXAMIDE.  .  By  Henry  L. 
Wheeler  and  Carl  O.  Johns.  (American  Chemical 
Journal,  1908,  XL,  233). 

SYNTHESIS  OF  SOME  BENZYL  DERIVATIVES  OF  URACIL  AND 
THYMINE.  By  Treat  B.  Johnson  and  John  H.  Derby, 
Jr.  (American  Chemical  Journal,  1908,  XL,  444). 

SYNTHESIS  OF  NEW  DERIVATIVES  OF  S-HYDROXYURACIL  (ISO- 
BARBITURIC  ACID.  By  Treat  B.  Johnson  and  D.  Breese 
Jones.  (American  Chemical  Journal,  1908,  XL,  538). 


8  CONTENTS 

THE  THIO  DERIVATIVES  OF  URACIL  AND  THE  PREPARATION  OF 

URACIL   IN   QUANTITY.     By   Henry   L.   Wheeler   and 

Leonard    M.    Liddle.      (American    Chemical    Journal, 

1908,  XL,  548). 
ON  THE  FORMATION  OF  PURINE  DERIVATIVES  FROM  4-METHYL- 

CYTOSINE.     By  Carl  O.  Johns.      (American  Chemical 

Journal,  1909,  XLI,  58). 
SYNTHESIS  OF    I-METHYL-S-HYDROXYURACIL.     By   Treat   B. 

Johnson   and  D.   Bresse  Jones.       (Journal    American 

Chemical  Society,  1909,  XXXI,  591). 
THE  PREPARATION  OF  S-METHYL-  AND  S-BENZYLURACIL.     By 

Henry  L.  Wheeler  and  Treat  B,  Johnson.     (American 

Chemical  Journal,  1909,  XLII,  30). 
THE   PREPARATION   OF    1,   4-DiMETHYLURACiL   AND   OF   THE 

MONOBENZYL    DERIVATIVES    OF    4-METHYLURACIL.         By 

Henry  L.  Wheeler  and  David  F.  McFarland.     (Ameri- 
can Chemical  Journal,  1909,  XLII,  101). 
SULPHUR   DERIVATIVES  OF   S-HYDROXYURACIL  :   PREPARATION 

OF     5-BENZYLMERCAPTOURACIL     AND     5-BENZYLMERCAP- 

TOCYTOSINE.     By  Treat   B.   Johnson  and   Herbert   H. 

Guest.    (American  Chemical  Journal,  1909,  XLII,  271). 

DIMETHYL  DERIVATIVES  OF  2-AMiNOPYRiMiDiNE.  PREPARATION 

OF    2-METHYLAMINO-5-METHYLPYRIMIDINE.       By    Treat 

B.  Johnson  and   Kenneth  G.   Mackenzie.      (American 

Chemical  Journal,  1909,  XLII,  353). 
THE  ACTION  OF  METHYL  IODIDE  AND  OF  BENZYL  CHLORIDE 

UPON     2-OXY-4-METHYL-6-METHYLMERCAPTOPYRIMID- 

INE.     By  Henry  L.  Wheeler  and  David  F.  McFarland. 

(American  Chemical  Journal,  1909,  XLII,  431). 
SYNTHESIS  OF  S-CYANURACIL.    By  Treat  B.  Johnson.    (Ameri- 
can Chemical  Journal,  1909,  XLII,  505). 
THE  THIO  DERIVATIVES  OF  THYMINE  AND  THE  PREPARATION 

OF  THYMINE.     By  Henry  L.  Wheeler  and  David   F. 

McFarland.   (American  Chemical  Journal,  1910,  XLIII, 

19). 

ON  SOME  PICROLONATES.    By  Henry  L.  Wheeler  and  George 
S.   Jamieson.      (Journal   of  Biological   Chemistry,   1908, 

IV,  111). 


APPENDIX 

Bibliography  of  Pyrimidine  Literature. 


[REPRINTED  FROM  THE  AMERICAN  CHEMICAL  JOURNAL.    VOL.  XX.    No.  6. 
JUNE,  1898.] 


Contributions  from  the  Sheffield  Laboratory  of  Yale  University. 

LX.—  RESEARCHES  ON   THE   CYCLOAMIDINES  : 
PYRIMIDINE  DERIVATIVES. 

BY  H.  I,.  WHEELER. 

For  convenience   of  reference,    in  this  work,  those   com- 
pounds which  have  the  amidine  formation 


in 
NXR'—  -1 

i  ___  i 
in 

in  which  two  of  the  radicals  R,  R',  and  R"  are  replaced  by  a 
ring  structure  or  a  bivalent  grouping,  are  referred  to  as  cyclo- 
amidines.  The  dotted  lines  in  the  above  formula  show  the  three 
possible  ways  of  replacing  the  radicals,  and  they  indicate  three 
forms  of  cycloamidines.  It  will  be  noticed,  however,  that  III 
is  the  tautomeric  form  of  I.  The  tautomeric  form  of  II  being 
obtained  when  the  position  of  the  hydrogen  X  is  changed  to 
the  opposite  nitrogen  atom.  There  are  therefore  only  two 
types  of  cycloamidines,  each  type  having  a  pseudomeric  or 
tautomeric  form  as  in  the  case  of  the  simple  amidines. 

The  first  type,  which  contains  only  one  of  the  nitrogen 
atoms  in  the  ring  is  represented  by  such  compounds  as 
a-aminoquinoline,  the  <*-aminobenzoxazines,  etc. 

The  second  type,  with  both  nitrogen  atoms  in  the  ring  struc- 
ture, is  found  in  the  anhydro  bases,  glyoxalines,  lophin,  etc. 

Then,  further,  combinations  of  these  types  and  their  tauto- 
meric forms  occur  :  The  cyanalkines,  <*-amino-  and  anilido- 
pyrimidines,  aminoquinoxalines,  cyanuramide,  dicyanortho- 
phenylenediamines,  and  the  like,  are  examples  of  the  com- 
bination types. 


482  Wheeler. 

The  object  of  the  work,  of  which  this  paper  gives  a  pre- 
liminary account,  is  primarily  to  investigate  the  action  of 
alkyl  halides  on  some  of  these  cycloamidines  which  have  not 
yet  been  examined  in  this  respect,  and  also  to  compare  this 
action  in  general  with  that  of  the  simple  amidines. 

Pechmann1  assumes  that  when  a  simple  amidine,  repre- 
sented by  the  general  formula  above,  is  acted  on  with  alkyl 
iodides,  the  hydrogen  X  is  directly  replaced,  and  hence  this 
reaction  serves  to  determine  structure. 

It  seems  to  the  writer  that  alkyl  iodides  may  be  added 
either  to  the  amido  group  or  to  the  imido  group  or,  when  the 
substituents  are  similar,*  to  both  and  perhaps  to  the  atoms 
joined  by  double  union.  In  two  of  the  latter  cases  an  ami- 
dine  would  result  of  a  different  structure  from  that  obtained 
by  direct  substitution,  so  that  this  method  of  determining 
structure  seems  to  be  not  without  objection. 

The  cycloamidines,  in  general,  unite  with  alkyl  iodides  and 
a  number  of  cases  have  been  described  among  those  of  the 
first  type,  where  no  direct  substitution  or  replacement  of  hy- 
drogen in  the  amino  group  takes  place,  at  least  not  as  the 
first  step  of  the  reaction.  To  illustrate  this  the  following  may 
be  cited  :  Thiele  and  Ingle3  obtained  dialkylaminotetrazols 
by  the  action  of  alkyl  iodides  on  aminotetrazol.  They  be- 
lieve that  in  these  only  one  of  the  alkyl  groups  replaces  hy- 
drogen of  the  amino  group.  Claus4  shows  that  a-amino- 
quinoline  takes  up  alkyl  iodides  in  the  same  manner  as  the 
quinoline  and  pyridine  bases  in  general,  and  that  the  amino- 
hydrogen  is  not  substituted.  Again,  K.  v.  Meyer5  has  shown 
in  several  cases  that  the  cyanalkines  form  similar  addition- 
products,  the  amino  group  not  being  substituted. 

Even  acyl  chlorides  add  to  the  cyanalkines  without  substi- 
tuting the  amino  group.  Herfeldt6  found  that  cyanbenzylin 
or  aminophenyldibenzylmiazin  unites  with  acetyl  and  benzoyl 

1  Ber.  d.  chem.  Ges.,  28,  2362  and  869. 

2  Pechmann  (loc.  cit.)  found  that  when  the  substituents  are  similar  radicals,  the 
amidine  gave  two  isomeric  alkylated  products.    This  is  precisely  what  would  be  ex- 
pected if  the  action  is  one  of  addition.    There  being  in  that  case  no  decided  tendency 
to  addition  entirely  to  either  one  of  the  nitrogen  atoms. 

8  Ann.  Chem.  (Liebig),  287,  249.  *  J.  prakt.  Chem.,  17,  209. 

*  Ibid.  22,  *66,  and  39,  265.  6  ibid.  [2],  53,  249. 


Researches  on  the  Cycloamidines .  483 

chlorides  to  form  well  crystallized  addition- products,  and  that 
an  acetyl  or  benzoylcyanbenzylin  was  not  obtained.  In  these 
cases  it  is  a  tertiary  nitrogen  which  is  the  point  of  attack  or 
addition. 

The  action  of  alkyl  iodides  on  the  cycloamides  of  the  second 
type  is  that  of  addition  also,  and,  as  in  the  case  of  the  simple 
amidines,  this  action  has  generally  been  considered  to  be  a 
direct  replacement  of  hydrogen,  since  by  treating  the  addi- 
tion-product with  alkali  alkyl  compounds  result.  The  same 
question  arises  here  as  in  the  case  of  the  simple  amidines. 
That  the  alkyl  group  invariably  replaces  the  hydrogen,  how- 
ever, has  not  been  proved.  It  is  not  improbable  that,  like  the 
cycloamidines  of  the  first  class,  it  is  the  tertiary  nitrogen 
that  unites  with  the  alkyl  halide. 

The  writer  has  found  that  phenylmethylanilidopyrimidine 
acts  with  methyl  and  ethyl  iodides  forming  stable  addition- 
products,  and  that  no  substitution  takes  place,  that  the  alkyl 
iodide  unites  with  one  of  the  tertiary  nitrogen  atoms  of  the 
ring  and  not  with  the  anilido  group  follows  in  all  probability 
from  the  behavior  of  these  products  with  alkali  : 

C17H1BN8.CH8I  +  NaOH  =  C1TH16NS  +  CH3OH  +  Nal. 

That  is,  methyl  alcohol  and  sodium  iodide  are  quantitatively 
formed,  and  unaltered  anilidopyrimidine  is  regenerated. 
The  formula  that  appears  most  probable  for  these  addition- 
products  is  therefore  either  I  or  II,  and  from  analogy  a  simi- 
lar structure  might  be  expected  in  the  case  of  the  alkyl  halo- 
gen addition-products  of  the  simple  amidines.1 

i  The  fact  that  the  alkyl  iodide  addition-products  of  the  simple  amidines  give  up 
hydrogen  iodide  and  not  the  alkyl  group  as  above  cannot  be  considered  as  showing 
that  the  addition  takes  place  to  the  — NH —  group  of  the  amidine.     To  be  sure,  the 
H 

grouping  N  would  be  expected  to  give  up  hydrogen  iodide,  and  those 

CH/    \ 

alkyl  iodide  addition-products  of  the  cyloamidiues  which  do  not  separate  hydrogen 
iodide  most  probably  do  not  have  this  grouping.  But  it  cannot  be  maintained  that 
because  an  addition-product  gives  up  hydrogen  iodide,  it  has  this  grouping. 


484  Wheeler. 

CH,  CHS 

1C  C 

\  /  %  /A 

CH3— N          CH  N          CH 

II  I  II  I 

C6H5C  C— NHCftHB  C6H5C          C— NHC6H5 

\  S  \// 

N  N 

/  \ 

CH3     I 

I  II 

R 

R"N=:C—  NHR' 

CH3     I 

III 

This  being  the  case,  the  structure  of  the  simple  amidines 
must  be  completely  revised,  and  the  opposite  or  so-called  tau- 
tomeric  structure  must  be  assigned  to  them.  At  any  rate,  no 
method  has  yet  been  devised  for  determining  the  structure  of 
the  amidines  in  question  that  is  without  objection. 

It  will  be  shown  below  that  phenylmethylpyrimidon,  a 
cycloamidine  of  the  second  type,  unites  with  one  molecule  of 
methyl  iodide  to  form  a  beautiful  crystalline  addition-product 
of  formula  IV  or  V. 

CH,  CH9 


I  C 

/  ^  \  /  \ 

N          CH  CH3— N         CH 

II  I  or  ||  | 

C6H5C          CO  C6H6C          CO 

N  N 

CH3I     H  H 

IV  V 

This  compound,  on  treatment  with  alkali,  gives  up  hydro- 
gen iodide  and  not  the  alkyl  group,  and  an  alkylated  pyrimi- 


Researches  on  the  Cycloamidines.  485 

don  results.  This  alkyl  derivative  differs  decidedly  from  the 
product  obtained  by  heating  phenylmethylchlorpyrimidine 
with  sodium  methylate.  The  alkyl  iodide  therefore  is  added 
to  one  of  the  nitrogen  atoms  of  the  pyrimidon  ring,  while 
Pinner1  found  that,  if  the  oxypyrimidine  is  heated  with  ethyl 
iodide  in  the  presence  of  alkali,  the  ethyl  group  attaches 
itself  to  oxygen. 

In  order  to  determine  to  which  nitrogen  the  alkyl  halide  is 
added,  a  synthesis  of  the  methylpyrimidon  was  attempted  as 
follows  :  Methylbenzamidine  hydrochloride  was  prepared. 
This,  with  acetoacetic  ester,  according  to  Pinner's  explana- 
tion of  the  formation  of  the  pyrimidines,  might  be  expected 
to  give  the  base  corresponding  to  formula  IV.  It  was  found, 
however,  that  methylbenzamidine  does  not  give  a  pyrimidine 
derivative  with  acetoacetic  ester,  at  least  not  under  the  same 
conditions  that  benzamidine  does,  so  that  for  the  present  the 
question  of  the  position  of  the  alkyl  group  must  be  left  unde- 
cided. 

Nef  has  shown  that  carbostyril  is  not  acted  on  by  ethyl 
iodide.  The  above  pyrimidon  differs  from  carbostyril,  in  its 
ring  structure,  in  having  a  tertiary  nitrogen.  It  would  seem 
most  probable  therefore  that  it  is  due  to  this  that  the  sub- 
stance takes  up  methyl  iodide  and  that  the  addition-product 
is  perhaps  best  represented  by  formula  V. 

Experimental  Part. 

N— C.CH, 

Phenylmethylanilidopyrimidine ,  C6H6C  CH          . — 

N— C— NHC6H5 

This  was  prepared  according  to  Pinner's3  directions  by  warm- 
ing phenylmethylchlorpyrimidine  with  aniline.  Instead  of 
purifying  the  material  by  dissolving  the  reaction-product  in 
alcohol  and  precipitating  it  with  ether,  it  was  found  best  to 
crystallize  it  directly  from  water,  precipitate  the  base  from 
the  hot  aqueous  solution  and  then  crystallize  this  from  ben- 
zene and  alcohol.  The  material  thus  obtained  crystallizes  in 

1  Die  Imidoather  und  ihre  Derivate,  p.  343.       [2  Ann.  Chem.  (Liebig),  276,  242. 
*  Die  Imidoather  und  ihre  Derivate,  p.  248. 


486  Wheeler. 

clusters  of  small  prisms  and  melts  at  i6o°-i6i°.  Pinner  gives 
its  melting-point  as  i5O°-i53°. 

The  hydrochloride  was  obtained  in  colorless  needles  melting 
at  240°  as  described  by  Pinner. 

The  hydrobromide  was  obtained  by  precipitating  the  base 
from  a  benzene  solution  with  hydrobromic  acid  gas.  It  forms 
minute  needles  when  crystallized  from  alcohol  and  it  melts  at 

250°. 

The  hydroiodide  forms  colorless  needles  melting  at  231°. 

Phenylmethylanilidopyrimidine  methyl  iodide. — Six  grams  of 
the  above  cycloamidine  were  heated  with  an  excess  of  methyl 
iodide  in  methyl  alcohol  solution  for  seven  hours  from  ioo°- 
105°.  The  material  was  then  washed  with  alcohol  and  crys- 
tallized from  water  and  alcohol.  Thus  obtained,  the  sub- 
stance melts  at  about  2io°-2i3°  with  strong  effervescence.  If 
suddenly  heated  it  melts  much  lower.  The  material  dried  in 
the  air  contains  2  molecules  of  water  of  crystallization. 
[Analysis  I.  and  II.]  When  dried  at  a  temperature  of  130°  it 
was  obtained  anhydrous  [Analysis  III.].  Determinations  I. 
and  III.  were  made  by  dissolving  the  substance  in  water  and 
precipitating  with  silver  nitrate.  Determination  II.  was  made 
by  the  method  of  Carius. 

Calculated  for  Found. 

Ci8H18N3I.2H30.     Ci8H18N,I.  I.  II.  III. 

I  28.9  31.5  28.8       28,7       31.5 

This  addition-product  is  readily  soluble  in  warm  water  and 
in  alcohol,  from  which  it  crystallizes  in  fine,  colorless  needles. 
Ammonia  or  alkali  immediately  precipitates  a  substance  melt- 
ing at  i6o°-i6i°,  which  has  all  the  properties  of  phenyl- 
methy  lanilidopy  rimidine . 

Phenylmethylmethylanilidopyrimidine, 
N— C— CH3 

C6H5C  GH  . — This  was  prepared  by  warming 

N— C— NCH8C6H5 

phenylmethylchlorpy rimidine  with  methyl  aniline.  It  is  the 
compound  that  should  result  by  treating  the  above  addition- 
product  with  alkali,  if  the  action  of  methyl  iodide  on  the 


Researches  on  the  Cycloamidines.  487 

cycloamidine  takes  place  by  substitution.  A  comparison  of 
the  above  with  the  following  properties  show  that  these  com- 
pounds are  different.  This  compound  crystallizes  from  alco- 
hol in  colorless  prisms  which  melt  at  113°.  It  dissolves 
readily  in  ether,  alcohol,  and  benzene,  but  is  insoluble  in 
water.  A  nitrogen  determination  gave  : 

Calculated  for 

C18H17NS.  Found. 

N  15.2  15.0 

This  compound  dissolves  readily  in  dilute  hydrochloric 
acid,  and  platinum  chloride  gives  a  bright  yellow,  granular 
precipitate,  which  melts  at  about  228°,  with  effervescence. 

The  hydroiodide  is  readily  soluble  in  warm  alcohol,  less 
readily  in  water.  It  melts  when  slowly  heated  at  about  198°. 
An  iodine  determination  gave  : 

Calculated  for 
C18H18N3I.2H3O.  Found. 

I  28.9  28.9 

The  nitrate  separates  from  dilute  nitric  acid  in  long,  color- 
less needles  or  prisms,  which  melt  with  violent  effervescence 
at  about  170°. 

Phenylmethylanilidopyrimidine  ethyl  iodide. — This  was  ob- 
tained when  5  grams  of  phenylmethylanilidopyrimidine  were 
heated  with  10  grams  of  ethyl  iodide  for  twelve  hours  at  120°- 
130°.  The  reaction -product  was  extracted  with  hot  water 
and  then  crystallized  from  alcohol,  when  it  separated  in  color- 
less needles  melting  at  about  215°.  When  crystallized  from 
water  the  material  shrivels  at  about  115°,  then  melts  with 
effervescence  at  or  near  215°.  An  iodine  determination  of 
air-dried  material  indicates  that  the  substance  separates  with 
i  molecule  of  water  of  crystallization.  [Analysis  I.]  The 
material  dried  at  I2o°-i3o°  becomes  anhydrous.  [Analysis 

no 

Calculated  for  Found. 

Ci9H20N8I.H20.  C,9HaoN3I.  I.  II. 

I  29.19  30.4  29.24       30.3 

This  addition-product  and  the  analogous  methyl  compound 
give  off  the  methyl  iodides  when  heated  to  their  melting- 
points.  Ammonia  or  alkali  precipitate  phenylmethylanilido- 
pyrimidine from  aqueous  or  alcoholic  solutions. 


488  Wheeler. 

Phenylmethylethylanilidopyrimidine, 

N—  C.CHS 
/          \ 
C6HtC  CH  .  —  This  was  prepared  like  the  cor- 

\          / 
N—  C—  N 


responding  methylanilidopyrimidine  for  the  sake  of  compari- 
son with  the  base  obtained  from  the  above  addition-product. 
It  is  an  entirely  different  base.  This  melts  at  87°  when  crys- 
tallized from  alcohol.  It  is  readily  soluble  in  hot  alcohol,  dif- 
ficultly in  cold,  and  insoluble  in  water.  It  separates  in  beau- 
tiful, long,  colorless  prisms.  A  nitrogen  determination  gave  : 

Calculated  for 

CI9H1(>N3.  Found. 

N  14.53  I4-56 

The  hydrochloride  is  difficultly  soluble  in  cold  water,  readily 
in  hot,  and  crystallizes  in  colorless  needles  which  appear  to  be 
hydrous.  On  heating  the  material  shrivels  at  about  100°, 
then  melts  at  about  210°. 

The  platinum  chloride  salt  separates  as  a  bulky,  light-yellow 
precipitate.  It  is  insoluble  in  hot  water,  and  melts  at  about 
218°. 

The  hydroiodide  crystallizes  in  prisms. 

An  attempt  to  prepare  an  ethyl  bromide  addition-product 
of  phenylmethylanilidopyrimidine  was  unsuccessful.  3.8 
grams  of  anilidopyrimidine  were  heated  with  an  excess  of 
ethyl  bromide  from  io2°-iO4°  for  five  hours,  when  the  material 
was  found  to  be  unaltered.  It  was  heated  again,  this  time 
with  the  addition  of  some  alcohol,  the  temperature  being  kept 
between  120°—  130°  for  seventeen  hours.  On  opening  the  tube 
then,  the  products  were  found  to  be  the  hydrobromide  of 
phenylmethylanilidopyrimidine  described  above,  and  ether. 
Ethyl  bromide,  therefore,  neither  effects  substitution  nor  ad- 
dition . 

Phenylmethylpyrimidon  methyl  iodide.  —  Phenylmethyloxy- 
pyrimidine  and  methyl  iodide,  4  grams  of  the  former  and  10 
of  the  latter,  were  heated  for  six  hours  at  100°.  No  reaction 
was  evident.  The  material  was  then  heated  for  nine  hours  at 


Researches  on  the  Cycloamidines.  489 

170°,  when  addition  took  place.  The  material  dissolved  al- 
most entirely  in  water  and,  on  concentrating  the  aqueous 
solution  to  a  syrup,  a  mass  of  needles  was  obtained.  This 
was  crystallized  from  alcohol  when  beautiful,  large,  colorless 
prisms  separated.  These  did  not  melt  sharply,  but  decom- 
posed with  effervescence  at  230°.  An  iodine  determination 
gave: 

Calculated  for 
CnHi0N3O.CH3I.  Found. 

I  38.7  38.6 

n-Methylphenylmethylpyrimidon. — When  the  above  com- 
pound with  methyl  iodide  was  dissolved  in  a  little  water  and 
dilute  alkali  was  added,  this  compound  separated  as  a  mass  of 
colorless  needles.  It  was  purified  by  crystallizing  from  water, 
when  it  separated  in  the  form  of  beautiful,  large  prisms,  which 
melt  at  about  gi°-g2°.  A  nitrogen  determination  gave  : 

Calculated  for 
Ci3HI3N,O.  Found. 

N  14.0  13.6 

This  compound  has  basic  properties  ;  it  dissolves  readily  in 
dilute  acids,  the  ordinary  salts  being  all  quite  soluble.  It  is 
readily  soluble  in  alcohol  and  ether,  less  readily  in  water,  and 
is  not  dissolved  by  a  small  amount  of  alkali.  The  nitrate  and 
platinum  chloride  double  salt  are  the  least  soluble  of  the 
ordinary  salts.  These  were  obtained  by  spontaneous  evapora- 
tion of  the  solutions. 

The  nitrate  crystallizes  in  colorless,  flattened  prisms  which 
melt  with  effervescence  at  about  195°. 

The  platinum  chloride  double  salt  separates  in  form  of  very 
large  prisms  with  the  color  of  azobenzene.  It  gave  no  definite 
melting-point  below  275°,  but  turned  dark  at  about  235°. 

Methylbenzamidine  hydrochloride,  C6H5C(NH)NHCH8.HC1. 
— This  was  prepared  by  dissolving  benzimidoethylester  hy- 
drochloride in  a  33  per  cent,  solution  of  methylamine.  On 
adding  the  hydrochloride  to  the  solution  of  the  amine  the  free 
ester  separates  ;  on  shaking  this  dissolves,  and  in  a  short 
time  a  mass  of  colorless  needles  separates.  This  material  was 
crystallized  from  water  in  which  it  is  not  extremely  soluble. 
A  chlorine  determination  gave  : 


49°  Wheeler. 

Calculated  for 

C8H10Na.HCl.  Found. 

Cl  20.82  20.75 

The  properties  of  this  amidine  hydrochloride  apparently 
differ  decidedly  from  those  of  the  corresponding  ethylami- 
dine.  Lessen1  prepared  ethylamidine  hydrochloride  in  a 
state  of  purity  only  with  some  difficulty,  while  Pinner*  ob- 
tained the  hydroiodide  as  an  oil  which  would  not  crystallize. 

NEW  HAVEN,  March,  1898. 


Ann.  Chem.  (Uebig)  265,  159.  2  Ber.  d.  chem.  Ges.ji,  7. 


I  REPRINTED  FROM  THE  AMERICAN  CHEMICAL  JOURNAL,  VOL.  XXIX,  No.  5, 
MAY,  1903.] 


Contributions  from  the  Sheffield  Laboratory  of  Yale  University. 

CII.— ON  SOME  CONDENSATION-PRODUCTS  OF  THE 
PSEUDOTHIOUREAS  :  SYNTHESIS  OF  URA- 
CIL,  THYMINE,  AND  SIMILAR  COM- 
POUNDS. 

BY  HENRY  I*.  WHEELER  AND  HENRY  F.  MERRIAM. 

Urea  and  thiourea  have  been  shown  to  undergo  condensa- 
tion with  a  variety  of  substances,  but  apparently  no  one  has 
attempted  to  use  the  simple  pseudothioureas  in  any  synthetic 
process  whatever.1 

The  pseudothioureas  in  question,  HN=C(SR) — NH,, 
(R=rCH8—  or  C2H6— ) ,  have  not  been  isolated.  Their  halogen 
hydride  salts  result  from  the  addition  of  alkyl  halides  to  thio- 
urea. These  are  described  as  extremely  unstable  compounds, 
and  Claus2  states  that  when  the  ethyl  bromide  addition-prod- 

1  Rathke  has  shown  that  their  salts  give  guanidine  when  boiled  with  ammonia. 
Ber.  d.  chem.  Ges.,  17,  309  (1884). 

»  Ann.  Chem.  (Liebig),  179, 146  (1875). 


Condensation- Products  of  the  Pseudothioureas.          479 

uct  is  treated  with  alkali  it  decomposes  into  ethyl  rhodanide, 
ammonia,  and  hydrogen  bromide. 

In  the  case  of  the  methyl  iodide  addition- prod  uct,  Bernth- 
sen  and  Klinger1  found  that,  with  silver  oxide,  a  solution 
containing  a  strong  base  resulted,  which  gave  a  blue  color  to 
red  litmus.  This  base  was  supposed  to  be  a  hydroxyl  com- 
pound, H2NCSNH2.CH,OH,  which,  on  evaporating  in  a  desic- 
cator, decomposed.  The  ethyl  iodide  addition-product,  which 
Claus  describes  as  an  exceptionally  unstable  compound,2  un- 
der similar  treatment  with  silver  oxide  gave  a  strong  alka- 
line solution  which,  on  evaporation,  contained  cyanamide  (di- 
cyandiamide).  A  similar  decomposition  was  observed  when 
the  compounds  were  treated  with  mercuric  oxide. 

We  have  made  no  attempts  to  isolate  these  free  pseudothio- 
ureas,  but,  at  first,  in  order  to  obtain  an  idea  of  their  stability, 
we  treated  the  methyl  iodide  addition-product  in  aqueous  solu- 
tion with  an  excess  of  alkali  and  benzoyl  chloride,  and  ob- 
tained an  excellent  yield  of  the  corresponding  benzoylpseudo- 
thiourea,3  C6H5CON-C(SCH,)— NH2.  The  ethyl  bromide 
addition-product,  on  shaking  with  alkali  and  phenyl  mustard 
oil,  gave  a  good  yield  of  the  phenylpseudodithiobiuret, 

C.H6NHCSN=C(SC2H6)NH2. 

The  free  pseudothioureas  are,  therefore,  not  so  unstable  as 
one  might  be  led  to  believe  from  previous  work,  and,  owing 
to  their  strong  basic  nature, it  seemed  probable  that  they  would 
undergo  condensation  with  aldehyde  and  ketone  esters  more 
readily,  and  prove  more  reactive  in  general,  than  the  normal 
ureas.  This  we  have  found  to  be  the  case. 

Ernert*  states  that  urea  does  not  condense  with  the  substi- 
tuted acetoacetic  esters  or  with  benzoylacetic  ester.  Warm- 
ington,5  also,  was  unable  to  obtain  a  condensation  of  urea  and 
the  latter  ester,  in  aqueous  solution,  but  found  that  they  could 
be  condensed  in  the  dry  state  at  a  high  temperature. 

We  have  readily  obtained   such   condensations   with   the 

1  Ber.  d.  chem.  Ges.,  II,  493  (1878). 

*  Ibid.,  8,  41  (1875). 

8  J.  Am.  Chem.  Soc.,  aj,  293  (1901). 
«  Ann.  Chem.  (Uebig),  358,  362  (1890). 

*  J.  prakt.  Chem.,  [a],  47,  202  (1893). 


480  Wheeler  and  Merriam. 

pseudothioureas  at  ordinary  temperatures.  These  pyrimidine 
condensations,  which  are  analogous  to  Pinner's,1  take  place 
in  alkaline  solution  in  a  similar  manner  to  that  observed  by 
Michael  in  the  case  of  urea  with  acetoacetic  and  malonic  es- 
ters.* They  are  also  similar  to  Traube's  synthesis  of  pyrimi- 
dine derivatives  in  which  guanidine  and  ethyl  cyanacetate  are 
employed.8 

A  method  similar  to  that  of  preparing  methyluracil  by 
condensing  urea  with  acetoacetic  ester,  by  means  of  hydro- 
chloric acid,4  has  not  been  applied  to  the  preparation  of  ura- 
cil,  probably  on  account  of  the  ease  with  which  free  formyl- 
acetic  ester  passes  into  trimesic  ester.  On  the  other  hand,  the 
sodium  salt  of  formylacetic  ester  is  not  only  easily  prepared,5 
but  is  also  quite  stable,  and  we  have  found  that  it  readily  con- 
denses, in  aqueous  solution,  with  both  methyl-  and  ethyl- 
pseudothioureas,  giving  a  good  yield  of  the  corresponding 
methyl-  and  ethyl-mercaptouracils.  For  example,  with  methyl- 
pseudothiourea,  as  follows  :6 

NH2        C2H6OCO  NH— CO         C2H5OH 

CH3S— C       +  CH     =    CH3SC         CH  + 

II                         II                         II         II 
NH  NaOCH  N CH         NaOH 

In  order  to  obtain  a  practically  quantitative  yield  of  uracil 
from  these  compounds,  heating  with  acids  in  a  sealed  tube  is 
not  necessary.7  When  they  are  boiled  with  concentrated  hy- 
drochloric acid,  or  better  with  hydrobromic  acid,  they  evolve 
mercaptan  and  yield  uracil  as  follows  :  * 

NHCO  NH— CO 

II  II 

RS— C     CH  +  H,O     =     OC         CH  +  RSH. 

II      II  I          II 

N— CH  NH— CH 

1  "Die  Imidoather  u.  ihrc  Derivate,"  p.  209. 

2  J.  prakt.  Chem.,  35,  456  (1887). 
»Ber.  d.  chem.  Ges.,  33,  1371  (1900). 

*  Behrend  :  Ann.  Chem.  (Liebig),  339,  9  ;  251,  238. 

6  Wislicenus  :  Ber.  d.  chem.  Ges.,  ao,  2933  (1887). 

8  An  attempt  to  condense  urea  with  this  salt  gave  a  negative  result. 

1 1«ist  has  shown  that  2-methylmercapto-4-methyl uracil  gives  4-methyluracil 
when  heated  with  concentrated  hydrochloric  acid  at  180*.  Ann.  Chem.  (lyiebig),  336, 
12  (1886). 


Condensation- Products  of  the  Pseudothioureas .  481 

Emil  Fischer  and  Georg  Roeder1  have  recently  prepared  | 
uracil,  thymine,  and  other  pyrimidine  derivatives  by  means  of 
an  interesting  synthesis.     Their  method  consists  in  heating 
urea  with  unsaturated  acids  and  brominating  the  hydroura- 
cils  thus  formed.     The  bromine  derivatives   are  then   con- 
verted  into   uracils  by  treatment  with   alkali   or  pyridine. 
This  synthesis  has  the  disadvantage  that  the   unsaturated 
acids  are  not  in  all  cases  easily  accessible  compounds,  and  the 
yields,  especially  in  the  case  of  uracil,  are  below  those  ob-j 
tained  by  our  method. 

Uracil  prepared  by  our  method  agreed  in  all  respects  with 
the  description  given  by  Fischer  and  Roeder.  We  have  found 
that  sodium  acetoacetic  ester  and  pseudomethylthiourea  give 
2-methylmercapto-4-methyluracil,  which  L,ist2  has  prepared 
by  a  different  method.  This,  on  boiling  with  hydrobromic 
acid,  gave  Behrend's3  4-methyluracil. 

The  isomeric  2-methylmercapto-5-tnethyluracil  and  5- 
methyluracil,  or  thymine,  were  obtained  in  a  similar  manner. 
Free  ethyl  formylpropionate  directly  condensed  with  pseudo- 
methylthiourea, and  the  sodium  salt  was  also  caused  to  react 
with  the  pseudothiourea : 

NH2       C2H5OCO  NH— CO  C,H5OH 

CH3SC        +  C.CH3  =  CH3SC         CCH8  + 

II  II  II    '       II 

NH  HOCH  N CH  H2O 

On  boiling  this  mercapto  derivative  with  hydrochloric  acid 
we  obtained  thymine,  which  was  identical  in  all  respects  with 
the  natural  product  obtained  from  the  nucleic  acid  of  the 
spleen,  a  sample  of  which,  through  the  kindness  of  Dr.  P.  A. 
Levene,  was  sent  to  us  for  comparison.  When  the  samples 
were  mixed  the  melting-point  was  not  altered. 

With  the  sodium  salt  of  ethyl  benzoylacetate  and  pseudo- 
methylthiourea we  obtained  2-methylmercapto-4-phenyluracil, 
which  was  converted  by  acids  into  4-phenyluracil,  identical 
with  the  phenyluracil  described  by  Fischer  and  Roeder. 

1  Her.  d.  chem.  Ges.,  34,  3751  (1901). 
9  Ann.  Chem.  (Uebig),  336,  12  (1886). 
s  Ibid.,  339,  8. 


482  Wheeler  and  Merriam. 

With   ethyl  methylacetoacetate    and   pseudoethylthiourea 
we   prepared   2-ethylmercapto-4,5-dimethyl-6-oxypyrimidirie, 
which  gave  a  new  dimethyluracil  (4,5-dimethyluracil)  : 
NH— CO  NH— CO 

II  II 

C3H5SC         CCH3        —         OC         CCH$. 

II         II  I  II 

N CCH3  NH  — CCHS 

With  ethyl  ethyl-acetoacetate  we  prepared  2-methyl- 
mercapto-4-methyl-5-ethyl-6-oxypyrimidine  and  4-methyl-5- 
ethyluracil.  L,ike  urea,1  pseudomethylthiourea  readily  con- 
denses with  acetylacetone  and  two  products  are  formed.  It 
condenses  also  with  ethyl  cyanacetate. 

Beside  the  above  condensations,  which  involve  an  attach- 
ment to  the  two  nitrogen  atoms  of  the  pseudothiourea,  an- 
other type  occurs  in  which  only  one  nitrogen  and  the  mer- 
capto  group  take  part.  For  example,  amino  acids  react  with 
the  pseudothioureas  in  aqueous  solution  to  form  guanidine 
acids  : 

HN=C— (NH2)— SR  +  H2NCH3COOH  = 

HN=C— (NH2)—  NHCH2COOH  +  RSH. 

Since  by  appropriate  treatment  these  compounds  can  be  con- 
verted by  loss  of  water  into  the  corresponding  rings,  it  seems 
probable  that  the  isocreatinine  obtained  by  Thesen2  from  fish 
flesh  (haddock)  may  be  prepared  by  this  method,  using 
N-methylpseudomethylthiourea  and  aminoacetic  acid. 

We  wish  to  reserve  the  study  of  the  condensation-products 
of  the  pseudothioureas  for  this  laboratory. 

EXPERIMENTAL  PART. 

Our  experiments  with  the  pseudothioureas  have  been  con- 
fined to  pseudomethyl-  and  pseudoethylthiourea. 

Pseudomethylthiourea  hydriodide  was  prepared  by  moisten- 
ing finely  powdered  thiourea  with  alcohol  and  then  adding  an 
excess  of  methyl  iodide.  Heat  was  evolved  so  that  a  con- 
denser was  necessary.  After  standing  twelve  hours,  ether 

1  Evans  :  J.  prakt.  Chem.,  48,  489  (1893). 

8  Hoppe-Seyler  :  Ztschr.  physiol.  Chem.,  34,  4  (1898). 


Condensation- Products  of  the  Pseudothiourcas .          483 

was  added  and  the  residue  filtered,  washed  with  ether,  and 
dried.  The  crude  addition-product  thus  prepared  was  used 
in  the  following  experiments. 

Pseudoethylthiourea  hydrobromide,  for  use  in  these  condensa- 
tions, can  be  conveniently  prepared  from  thiourea  containing 
considerable  ammonium  thiocyanate  ;  that  is  to  say,  from  the 
product  obtained  by  heating  ammonium  thiocyanate  at  170° 
for  forty-five  minutes1  and  then  crystallizing  once  or  twice 
from  water.  The  thiourea  is  powdered,  moistened  with  alco- 
hol, and  an  excess  of  ethyl  bromide  added.  On  boiling  this 
mixture  for  four  or  five  hours  the  greater  part  of  the  mass  dis- 
solves, leaving  ammonium  bromide  as  an  insoluble  residue. 
The  solution  is  then  filtered  and  most  of  the  alcohol  evapora- 
ted. The  oil  thus  obtained  is  transferred  to  a  distilling-bulb 
and  the  ethyl  rhodanide  distilled  off  under  diminished  pres- 
sure on  the  water-bath.  The  residue,  on  cooling,  solidifies  to 
a  crystalline  mass,  which,  after  drying  on  paper  in  the  air, 
melts  at  about  88°  and  is  pure  enough  for  use  in  the  following 
experiments : 

NHCO 

2-Methylmcrcapto-6-oxypyrimidinc>  CH3SC     CH. — In   this 

II      II 
N— CH 

preparation  the  crude  sodium  salt  of  formylacetic  ester*  was 
considered  as  70  per  cent  pure.3 

Seven  grams  of  sodium  hydrate  were  dissolved  in  70  cc. 
of  water  and  38  grams  of  the  methyl  iodide  addition-product 
of  thiourea  were  added,  and  then  29  grams  of  sodium  formyl- 
acetic ester.  The  mixture  was  allowed  to  stand  for  twelve 
hours  at  ordinary  temperature,  then  warmed  on  the  water- 
bath  for  a  few  minutes,  cooled,  and  acidified  with  acetic  acid. 
The  crystalline  precipitate  thus  produced  was  filtered,  washed, 
and  dried.  It  weighed  11.3  grams,  a  yield  of  46  per  cent, 
calculating  from  the  methyl  iodide  addition-product.  It  crys- 
tallized from  water  in  long  prisms,  or  short,  lozenge-shaped 

1  Reynolds  and  Werner  :  J.  Chetn.  Soc.  (Condon),  83,  i  (1903). 

2  Wislicenug  :  Ber.  d.  chem.  Ges.,  ao,  2933. 
•  Von  Pechmann  :  Ibid.%  as,  1047. 


4 84  Wheeler  and  Merriam . 

tablets,  and  the  surfaces  of  the  crystals  were  generally  etched. 
It  is  quite  soluble  in  alcohol  and  acetone,  and  it  melts  at  198* 
to  199°.  A  nitrogen  determination  gave  : 

Calculated  for 
C6H6ON2S.  Found. 

N  19.72  19.86 

NH— CO 

I  I 

2-Ethvlmercapto-6-oxypyrimidine,    C2H5SC         CH.  — Fifty- 
It          II 
N CH 

nine  grams  of  the  ethyl  bromide  addition-product  of  thiourea 
were  treated  with  one  molecular  proportion  of  sodium  hydrate 
in  10  per  cent  aqueous  solution,  and  then  40  grams  of  formyl- 
acetic  ester  were  added.  After  standing  for  twenty-four  hours 
the  solution  was  divided  into  two  equal  portions.  One, 
after  warming  on  the  water-bath  until  effervescence  stopped, 
was  cooled  and  immediately  acidified  with  acetic  acid.  This 
gave  6.3  grams  of  the  mercapto  derivative.  The  other  por- 
tion was  allowed  to  stand  for  a  week.  On  acidifying  then, 
6.1  grams  of  the  mercapto  compound  were  obtained,  a  yield  of 
32  per  cent  of  the  calculated.  In  another  experiment  25 
grams  of  the  ethyl  bromide  addition-product  were  dissolved  in 
more  dilute  alkali,  namely,  5.5  grams  of  sodium  hydrate  in 
95  cc.  of  water,  and  27  grams  of  sodium  formylacetic  ester 
were  added.  After  two  hours'  standing,  one-half  of  the  solu- 
tion was  warmed,  cooled,  and  acidified  with  acetic  acid, 
whereupon  5  grams  of  the  mercapto  compound  separated. 
After  standing  two  days  the  remaining  portion  gave  4.9  grams 
of  the  condensation-product,  a  yield  of  47  per  cent  of  the  cal- 
culated. 

It  is  evident  from  this  that  the  materials  react  in  a  short 
time,  and  that  long  standing  does  not  influence  the  yield. 
The  reaction  possibly  involves  an  addition  similar  to  that  in 
the  case  of  acetoacetic  ester  and  urea1,  since  it  frequently  hap- 
pens that  these  mixtures  can  stand  for  several  days,  and  then, 
if  the  solution  is  not  warmed  before  acidifying,  no  precipita- 
tion whatever  occurs.  Moreover,  the  fact  that  usually  a  yield 

1  Behrend  and  Ernert :  Ann.  Chem.  (I,iebig),  258,  360  (1890). 


Condensation- Products  of  the  Pseudothioureas .  485 

approximating  only  one-half  the  calculated  is  obtained  may 
also  possibly  be  accounted  for  by  the  assumption  that,  like  urea 
and  acetoacetic  ester  in  alkaline  solution,  2  molecules  of  the 
ester  react  with  only  one  of  the  pseudothiourea. 

In  one  experiment,  however,  5  grams  of  the  ethyl  bromide 
addition-product,  i.i  grams  of  sodium  hydrate,  and  6  grams 
of  the  sodium  salt  in  10  cc.  of  water,  on  standing  over  night, 
gave  2.9  grams  of  the  condensation-product,  a  yield  of  68.8 
per  cent  of  the  calculated.  On  crystallizing  from  10  cc.  of 
alcohol,  1.75  grams  of  pure  ethylmercaptooxypyrimidine  sepa- 
rated at  once.  This  substance  is  easily  soluble  in  warm  alco- 
hol and  hot  water,  difficultly  soluble  in  cold,  and  forms  beau- 
tiful, colorless,  small,  stout  prisms  and  pyramids  melting  at 
152°.  A  nitrogen  determination  gave: 

Calculated  for 

C4H8ON2S.  Found. 

N  17.94  17.93 

NH— CO 

Uracil,  OC         CH. — Fifteen  grams  of  the  above  methyl-  /• 

I          II 
NH— CH 

mercaptouracil  and  150  cc.  of  concentrated  hydrochloric  acid 
were  boiled  for  four  hours,  when  mercaptan  had  ceased  being 
evolved.  The  solution  was  evaporated  to  dry  ness  and  the 
residue,  after  drying,  weighed  11.9  grams  (94.4  per  cent 
yield).  It  melted  with  effervescence  at  335°  (on  an  Anschiitz 
thermometer  in  a  paraffin-bath),  and,  on  crystallizing  from 
water,  it  formed  balls  of  minute,  pure- white  needles,  which, 
on  rapidly  heating,  melted  at  338°.  By  holding  the  tempera- 
ture a  few  degrees  below  this  the  material  could  be  made  to 
melt.  It  agreed  in  properties  with  Fischer  and  Roeder's1 
preparation.  When  the  ethylmercapto  derivative  (1.5  grams) 
was  heated  in  a  closed  tube  with  concentrated  hydrochloric 
acid  (5  cc.)  for  four  and  one-half  hours,  about  0.05  gram  of 
an  insoluble  by-product  was  formed,  and  0.9  gram  of  pure 
uracil  was  obtained.  A  nitrogen  determination  gave  : 

i  Loc.  tit. 


486  Wheeler  and  Mertiam. 

Calculated  for 


Found. 

N  25.00  25.24 

One  hundred  parts  of  water  at  25°  dissolve  0.358  part  of 
uracil. 

Uracil  may  be  boiled  with  alkali  and  recovered  unaltered 
by  acidifying  the  solution.  The  alkaline  solution  probably 
contains  the  substance  as  a  salt  of  /?-uramidoacrylic  acid,  just 
as  Behrend's  methyluracil  gives  /?-uramidocrotonic  acid. 
When  uracil  is  dissolved  in  ammonia  and  most  of  this  re- 
moved by  boiling,  then  silver  nitrate  -is  added  and  the  solu- 
tion is  boiled,  an  amorphous  silver  salt  is  precipitated,  which 
is  soluble  in  an  excess  of  ammonia  and  nitric  acid.  The 
composition  of  the  salt  prepared  in  this  manner  varied.  One 
preparation  gave  63.8  and  64  per  cent  silver,  another  59.9  and 
60.  i  per  cent  silver,  while  the  calculated  for  silver  yff-urami- 
doacrylate  is  62.79  per  cent.  Uracil  does  not  form  a  picrate. 
5-Bromuradl.  —  Two  and  one-half  grams  of  uracil  were 
suspended  in  carbon  disulphide  and  3.8  grams  of  bromine 
were  added.  Hydrogen  bromide  was  slowly  evolved,  and  after 
two  days,  on  evaporating  to  dryness,  a  red  residue  was  ob- 
tained which,  on  warming  on  the  water-bath,  became  color- 
less. When  crystallized  from  water  it  formed  small,  stout, 
colorless  prisms,  and  when  heated  turned  dark  above  200°, 
and  melted  with  some  effervescence  at  about  293°.  A  nitro- 
gen determination  gave  : 

Calculated  for 
C4HsOaNaBr.  Found. 

N  14.66  14.60 

2-Methylmercapto-4.  •  methyl-6-oxypyrimidine, 
NH—  CO 

I  I 

CH3SC         CH     .  —  Sixteen  grams  of  the  methyl  iodide  addi- 

II  II 

N  -  CCH, 

tion-product  of  thiourea  were  dissolved  in  20  cc.  of  water  and 
added  to  a  cold  30  per  cent  solution  of  4.5  grams  of  potassium 
hydrate.  Nine  and  six-tenths  grams  of  acetoacetic  ester 
were  then  added  and  the  mixture  allowed  to  stand.  The 


Condensation- Products  of  the  Pscudothioureas .          487 

next  day  long  prisms  had  formed.  After  two  days  these  were 
filtered  and  found  to  weigh  5  grams.  This  material  was  sol- 
uble in  acids  and  alkali,  and  it  melted  at  219°,  the  melting- 
point  assigned  to  this  compound  by  List.  When  2  grams  of 
this  were  boiled  with  10  cc.  of  hydrobromic  acid  for  one  hour 
mercaptan  was  given  off  and  1.2  grams  of  Behrend's4-methyl- 
uracil  were  obtained. 

2-Methylmercapto-^-methyl-6-oxypyrimidine, 
NH— CO 

CH8SC        CCH3. —Sixty-five  grams  of  the  methyl  iodide  ad- 

I!        II. 
N CH 

dition-product  of  thiourea  were  treated  with  17  grams  of 
potassium  hydrate  in  150  cc.  of  water,  and  45  grams  of  sodium 
formylpropionic  ester  were  then  added.  The  mixture,  on 
standing  two  and  a  half  days,  was  filtered  from  some  sedi- 
ment and  neutralized  with  acetic  acid.  A  fine  crystalline 
precipitate  of  methylmercaptothymine  came  down,  which 
weighed  9.2  grams,  or  20  per  cent  of  the  calculated.  It  crys- 
tallized in  strings  of  small  plates  from  water,  in  which  it  is 
difficultly  soluble  when  hot  and  nearly  insoluble  when  cold. 
On  heating,  it  sintered  at  about  225°  and  melted  at  233°.  A 
nitrogen  determination  gave  : 

Calculated  for 

C«H8ON2S.  Found. 

N  17.94  17-95 

NH— CO 

•      I  I 

5-Methyluracil  (  Thymine) ,  OC         CCH3. — The  above  mer- 

I  II 

NH  — CH 

captothymine  reacted  less  readily  with  hydrochloric  acid  than 
in  the  other  cases.  Nine  and  two-tenths  grams  were  boiled 
with  100  cc.  of  concentrated  hydrochloric  acid  for  ten  hours, 
whereupon  no  more  mercaptan  was  given  off.  The  solution,  on 
evaporating,  then  gave  7.3  grams  of  crude  thymine  (melting  at 
319°),  which  is  99  per  cent  of  the  calculated.  This  crystal- 
lized from  water  in  small,  apparently  rectangular,  colorless 


488  Wheeler  and  Merriam. 

plates,  and  on  rapidly  heating  melted  at  326°  (on  an  An- 
schiitz  thermometer) .  Fischer  and  Roeder  state  that  their 
preparation  sintered  at  318°  and  melted  at  321°.  A  sample  of 
thymine  which  Dr.  P.  A.  L,evene,  of  the  Pathological  Institute 
at  Ward's  Island,  N.  Y.,  kindly  gave  us,  proved  to  be  identi- 
cal with  our  compound.  This  sample  was  obtained  from  the 
nucleic  acid  of  the  spleen,  and  on  mixing  it  with  some  of  our 
substance  the  melting-point  was  unchanged.  A  nitrogen  de- 
termination in  the  case  of  the  synthetic  product  gave : 

Calculated  for 

C5HeO2N2.  Found. 

N  22.22  22.36 

One  hundred  parts  of  water  at  25°  dissolve  0.404  part  of 
thymine. 

2-EthylmercaptO'4.  ^-dimethyl-  6-oxypyrimidinc , 
NH— CO 

I  I 

CjH5SC         CCH3. — Six  grams  of  potassium   hydrate   were 

II  II 

N CCH8 

dissolved  in  50  cc.  of  water  and  cooled.  To  this  was  added 
13  grams  of  the  ethyl  bromide  addition- product  of  thiourea 
and  then  10  grams  of  methyl  acetoacetic  ester.  The  oil  grad- 
ually disappeared  and  a  white  solid  was  formed.  After  stand- 
ing for  two  days  the  solution  was  made  slightly  acid  with  hy- 
drochloric acid  and  filtered.  The  precipitate  in  this  case 
proved  to  be  a  mixture.  On  boiling  with  about  30  cc.  of  alcohol 
and  filtering  while  hot,  a  separation  was  effected.  The  solu- 
ble portion  was  crystallized  from  a  mixture  of  alcohol  and 
ether.  It  formed  stout  prisms  melting  at  about  156°,  sinter- 
ing at  about  151,°  and  a  nitrogen  determination  gave  : 

Calculated  for 
C8HlaON2S.  Found. 

N  15.2  15.6 

The  compound  that  was  not  readily  dissolved  by  boiling 
alcohol  was  purified  by  crystallizing  it  from  a  large  amount  of 
alcohol.  It  was  found  to  be  free  from  sulphur,  and  on  heat- 
ing it  began  to  decompose  at  about  260°,  and  effervesced  at 
269"  to  270°,  turning  reddish-brown.  It  consisted  of  minute, 


Condensation- Products  of  the  Pseudothioureas .          489 

microscopic  crystals  that  formed  twins  having  the  form  of  a 
cross.  We  did  not  stop  to  determine  the  structure  of  this 
compound,  but  we  believe  that  possibly  it  is  acetomethyl- 
acetylcyanamide,  CH8CO(CHS)CHCONHCN.  A  nitrogen 
determination  agreed  with  the  calculated  for  this  formula. 

Calculated  for 

C«H802N,.  Found. 

N  20.00  20.03 

NH— CO 

I      I 

4.,5-Dimcthyluracil,  OC        CCH8. — About    i    gram   of  the 

I          II 
NH— CCH, 

above  ethylmercaptodimethyluracil  was  boiled  for  four  hours 
with  10  cc.  of  concentrated  hydrochloric  acid.  Mercaptan 
was  given  off  and  there  was  a  smooth  decomposition  into  the 
oxygen  derivative.  The  solution  was  evaporated  to  dry  ness 
and  the  residue  was  crystallized  twice  from  alcohol.  It  crys- 
tallized in  microscopic  needles  which  melted  to  a  clear  liquid, 
with  partial  decomposition,  at  292°.  A  nitrogen  determina- 
tion gave  : 

Calculated  for 

C«jH802N2.  Found. 

N  20.00  20.34 

2-Methylmcrc&pto-4.-methvl-5-cthyl-6-oxypyrimidine, 
NH— CO 

I  I 

CH.SC         C.C,H6.— Ten  grams  of  the  methyl  iodide  addi- 

II  II 

N C.CH, 

tion-product  of  thiourea  were  dissolved  in  a  solution  of  2.6 
grams  of  potassium  hydrate  (i  molecule)  in  20  cc.  of  water, 
and  to  this  7  grams  of  ethyl  ethylacetoacetate  were  added. 
A  little  alcohol  was  also  added,  and  finally  some  more  alkali, 
and  the  mixture  was  allowed  to  stand  for  a  week.  Solid  ma- 
terial gradually  separated,  which  was  filtered  after  neutral- 
izing the  solution.  The  yield  of  crude  material  was  3.2 
grams.  It  was  crystallized  from  alcohol,  from  which  it  sepa- 
rated in  long,  flat,  colorless  prisms  with  branching,  brush-like 


492  Wheeler  and  Merriam. 

drate,  and  precipitated  with  carbon  dioxide,  it  gave  0-benz- 
glycocyamidine.1 

Pseudomethylthiourea  Chloracetate , 

H2N—C(SCH8)  —  NH.C1CH,COOH.— Thirty-three  grams  of 
the  methyl  iodide  addition-product  of  thiourea  were  dissolved 
in  a  small  quantity  of  cool  alcohol,  and  a  concentrated  alco- 
holic solution  of  8.5  grams  of  potassium  hydrate  was  added. 
The  solution  was  filtered  from  potassium  iodide  and  then  14.5 
grams  of  chloracetic  acid  were  slowly  added.  Crystalline  ma- 
terial soon  separated  which,  on  drying,  weighed  17  grams. 
When  crystallized  from  alcohol  it  formed  transparent,  rec- 
tangular plates,  melting  at  162°.  It  was  very  soluble  in 
water.  A  nitrogen  determination  gave : 

Calculated  for 

C4H9OjN2SCl.  Found. 

N  15.17  15.26 

NEW  HAVEN,  CONN.,  Feb.  26, 1903. 
1  Griess  :  Ber.  d.  chem.  Ges.,  13,  977. 


[REPRINTED  FROM  THB  AMERICAN  CHEMICAL  JOURNAL,  VOL.  XXIX,  No.  5, 
MAY,  1903.] 


Contributions  from  the  Sheffield  Laboratory  of  Yale  University. 

CIIL  — SYNTHESES    OF    AMINOOXYPYRIMIDINES 

HAVING   THE  COMPOSITION  OF  CYTOSINE  : 

2-AMINO  6-OXYPYRIMIDINE  AND  2-OXY- 

6-AMINOPYRIMIDINE. 

BY  HENRY  L,.  WHEELER  AND  TREAT  B.  JOHNSON. 

The  interest  which  in  recent  years  has  been  attached  to  the 
study  of  pyrimidine  derivatives  has  been  increased  by  a  new 
discovery  of  Kossel  and  Steudel.  Working  with  a  large 
quantity  of  sturgeons'  testicles  they  obtained,  in  the  histidine 
fraction,  a  basic  substance  agreeing  in  composition  with  the 
formula  C4H5ON3.  Kossel  and  Steudel  state  their  belief  that 
this  compound  is  an  aminooxypyrimidine,2  since  hitherto  all 
of  the  nitrogen  compounds  obtained  from  nucleic  acid  have 
been  found  to  contain  the  pyrimidine  ring.  This  new  sub- 
stance was  found  to  closely  resemble  cytosine,  which  Kossel 
and  Neumann3  obtained  in  the  year  1894  as  a  cleavage-prod- 

2  Ztschr.  physiol.  Chem.,  37,  179  (1902). 

3  Ber.  d.  chem.  Ges.,  37,  2215  (1894). 


Syntheses  of  Aminooxypyrimidines . 


493 


uct  of  thymus  nucleic  acid.  Kossel  and  Steudel  have  recently 
undertaken  the  reinvestigation  of  thymus  cytosine  and  they 
now1  conclude  that  the  product  is  identical  with  sturgeon 
cytosine.  They  state  that  it  can  also  be  prepared  from  her- 
rings' testicles  and  call  attention  to  the  fact  of  its  wide  occur- 
rence in  animal  organs. 

Dr.  P.  A.  Levene  has  kindly  sent  us  the  proof  of  his  article 
on  "  Darstellung  und  Analyse  einiger  Nucleinsauren,"  in 
which  he  describes  the  preparation  of  this  base  from  the 
nucleic  acid  of  the  spleen  and  pancreas.2 

Kossel  and  Steudel3  conclude  that  material  yielding uracil  is 
widely  disseminated  in  animal  organs,  and  it  seemed  probable 
that  perhaps  uracil  results  from  the  cleavage  of  cytosine  by 
treatment  with  sulphuric  acid  at  high  temperatures.  More- 
over, they  state  in  their  last  paper4  that  cytosine,  by  the  action 
of  nitrous  acid,  gives  a  substance  having  the  properties  of 
uracil. 

From  this  it  appears  that  of  the  seven  theoretically  possible5 
aminooxypyrimidines,  the  first  to  be  considered  are  those  that 
would  be  expected  to  yield  uracil  by  the  above  treatment. 
An  examination  of  the  following  formulas  will  show  that  for- 
mulas I.  and  II.  are  the  only  ones  that  agree  with  this  be- 
havior : 


N=C— NH, 

CO     CH 

I          II 
NH— CH 

I. 

NH— CO 

!         I 
HC        C— NH2 


NH— CO 


NH—CH 


CO 

I 


III. 
N==CH 


C—  NH, 


HC         CH 


Hi 


COH 


N CH  N C— NH2  N C— NH, 

IV.  V.  VI. 

1  Ztschr.  physiol.  Chera.,  37,  379  (1903). 

8  To  appear  in  Ztschr.  physiol.  chein.,  38,  (1903).    See  also  Am.    J.  Physiol.,  8, 
XII  (1903);  J.  Am.  Chem.  Soc.,  25,  R.  188  (1903). 
37*«f.,  37,  347  (1903). 
4  Ibid.,  37,  380  (1903). 
6  Tautomeric  forms  are  not  considered. 


494  Wheeler  and  Johnson. 

N CH 

II  II 

H,N— C        COH 

I  I 

N=CH 

VII. 

We  have  now  prepared  the  two  aminooxypyrimidines  rep- 
resented by  formulas  I.  and  II.  and  we  find  that  both  products 
agree  closely  in  properties  with  the  descriptions  of  cytosine. 
Of  the  two  compounds,  2-oxy-6-amino-pyrimidine,  formula  I., 
agrees  better  than  the  isomer,  2-amino-6-oxypyrimidine. 
Formula  II.,  in  fact,  seems  to  be  excluded  as  representing 
cytosine  chiefly  because  this  compound  crystallizes  from  water 
in  anhydrous  crystals.  Its  picrate  melts  a  little  higher  than 
the  melting-point  given  for  cytosine  picrate,  but  in  other  re- 
spects the  salts  are  closely  similar. 

On  the  other  hand,  2-oxy-6-aminopyrimidine  crystallizes 
with  i  molecule  of  water  of  crystallization,  like  cytosine,  and 
its  properties  agree  in  practically  every  respect,  as  far  as  can 
be  judged,  with  the  descriptions  of  the  natural  substance. 
The  picrate,  when  prepared  from  the  pure  base,  has  a  higher 
decomposing-point  than  that  given  for  the  picrate  from 
natural  cytosine.  However,  we  are  inclined  to  believe  that 
our  base  and  cytosine  are  identical  and,  therefore,  the  structure 
of  cytosine  is  to  be  represented  by  formula  I.1  It  will  be 
necessary  to  compare  our  material  with  the  natural  before 
this  can  be  definitely  settled,  and  we  hope  soon  to  obtain  a 
sample  of  the  natural  substance. 

When  2-oxy-6-aminopyrimidine  was  heated  with  20  per 
cent  sulphuric  acid  for  3  hours  at  150°- 170°  it  was  found  that 
15  per  cent  of  the  material  was  converted  into  uracil.  Dr. 
Osborne  informs  us  that  to  obtain  uracil  it  was  necessary  to 
heat  triticonucleic  acid  with  acids  for  a  considerable  time.2 

Since  uracil  results  from  the  cleavage- cytosine,  the  natural 

1  The  substance  can  naturally  be  viewed  as  a-oxy-4-aminopyrimidine,  and,  on  ac- 
count of  the  usual  nomenclature,  this  aspect  better  illustrates  its  character  as  a  sort 
of  hydrated  fragment  of  uric  acid.    Its  relation  to  uracil,  however,  is  better  shown 
by  representing  the  substance  as  a  6-amino  derivative  or  the  tautomeric  6-imino 
form. 

2  See  Report  Conn.  Agr.  Expt.  Sta.  for  1901  p.  409. 


Syntheses  of  Aminooxypyrimidines .  495 

assumption  is  that  the  analogous  thy  mine,  which  until  re- 
cently has  been  more  widely  obtained  as  a  cleavage-product, 
results  from  the  decomposition  of  a  corresponding  base,  the 
as  yet  undiscovered  5-methylcytosine,  this  base  undergoing 
cleavage  more  readily  than  cytosine.  We  intend  to  give  an  ac- 
count of  this  new  base  later,  the  preparation  of  these  bases 
being  one  of  the  first  steps  toward  the  synthesis  of  the  nucleic 
acids. 

We  prepared  the  synthetic  cytosine  as  follows  :  The  ethyl 
bromide  addition-product  of  thiourea  was  treated  with  i 
molecule  of  alkali  in  aqueous  solution  and  the  sodium  salt 
of  ethyl  formylacetate  added.  On  standing  a  number  of  hours, 
then  warming  for  a  few  minutes,  cooling,  and  acidifying  with 
acetic  acid,  2-ethylmercapto-6-oxypyrimidine  was  obtained  : 

NH2         C2H5OCO  NH— CO          C2H5OH 

C2H5SC        +  CH     =     C2H6SC        CH   + 

II  II  II         II 

NH  NaOCH  N CH         NaOH 

The  2-ethylmercapto-6-oxypyrimidine  was  converted  into 
2-ethylmercapto-6-chlorpyrimidine  by  means  of  phosphorus 
pentachloride  and  the  phosphorus  oxychloride  was  removed 
by  evaporation  in  a  vacuum. 

NH— CO  Nr=CCl 

I  I  I 

CH  +  PC16  =  C2H5SC         CH  +  POC1,  +  HC1. 

II          II                                    II          II 
N CH  N CH 


,1.1 

<Hsd          ' 

r^njVJW 


When  2-ethylmercapto-6-chlorpyrimidine  was  heated  with 
alcoholic  ammonia  it  gave  2-ethylmercapto-6-aminopyrimi- 
dine. 

N CC1  N C— NH2 

C2H5SC         CH  +  2NH8    =    C2H5SC          CH 

II          II                                         II          II 
N CH  N CH 

Finally  the  2-ethylmercapto-6-aminopyrimidine  was  con- 
verted into  the  2-oxy-6-aminopyrimidine  by  boiling  with  hy- 
drobromic  acid  : 


496  Wheeler  and  Johnson. 


N=C—  NH2  N  -  C—  NH2 

II  II 

C2H6SC          CH  +  H20  =  OC          CH         +  C2H5SH. 

II  II  I  II 

N  -  -CH  NH  —  CH 

The  synthesis  of  2-araino-6-oxypyrimidine  was  effected  by 
treating  sodium  formylacetic  ester  with  free  guanidine  in 
aqueous  solution,  whereupon  the  following  condensation  took 
place  : 

NH2        C2H6OCO  NH—  CO         C2H6OH 

H2N—  C       +  CH     -     H2N—  C         CH  + 

II  II  II          II 

NH  NaOCH  N  -  CH         NaOH 

Sodium  formylacetic  ester  is  easily  prepared  by  treating 
equal  weights  of  ethyl  formate  and  ethyl  acetate,  in  two  vol- 
umes of  ether,  with  metallic  sodium,  according  to  the  direc- 
tions of  Wislicenus.1 

EXPERIMENTAL,  PART. 

NH—  CO 

2-Ethylmcrcapto-6-oxypyrimidine,    C2H,SC         CH.  --  This 

'    II          II 
N  -  CH 

compound  has  been  described  in  the  preceding  article  by 
Wheeler  and  Merriam.  We  have  usually  taken  50  grams  of 
the  ethyl  bromide  addition-product  of  thiourea,3  dissolved  in 
10  per  cent  sodium  hydrate,  and  have  then  added  somewhat 
over  the  calculated  quantity  of  dry  sodium  ethyl  formylacetate. 
After  standing  for  two  or  three  hours  the  solution,  heated  to 
boiling  and  then  cooled,  was  acidified  with  acetic  acid.  A 
yield  of  about  48  per  cent  of  the  calculated  of  crude  mercap- 
tooxypyrimidine  was  usually  obtained. 

N  -  CC1 

I  I 
2-Ethylmercapto-6-chlorpyrimidine,  C2H5SC          CH.-When 

II  II 
N  -  CH 

1  Ber.  d.  chem.  Ges.,  ao,  2933  (1887). 

2  Claus  :  Ann.  Chem.  (I^iebig),  179,  145. 


Syntheses  of  Aminooxypyrimidincs.  497 

2-ethylmercapto-6-oxypyrimidine  (5.3  grams)  and  phos- 
phorus pentachloride  (7.5  grams)  were  warmed  on  the  steam- 
bath  they  reacted  smoothly  and  hydrogen  chloride  was  given 
off.  The  product  was  an  oil.  An  attempt  to  purify  it  by  dis- 
tilling off  the  phosphorus  oxychloride  at  ordinary  pressure  in 
an  oil-bath,  at  150°,  caused  decomposition.  It  was  found 
that  the  oil  could  be  distilled  in  steam,  but  the  greater  part  was 
converted  into  uracil  by  this  treatment.  The  portion  purified 
in  this  manner  (2  grams)  was  analyzed  with  the  following  re- 
sult : 

Calculated  for 
CeH7N2SCl.  Found. 

N  16.04  J6.8 

The  oil>  when  dry,  is  stable  at  150°.  When  boiled  with 
hydrochloric  acid  it  gives  uracil.  The  chlorpyrimidine,  for 
conversion  into  the  amino  derivative,  was  prepared  as  follows  : 
6.3  grams  of  2-ethylmercapto-6-oxypyrimidine  and  8.5  grams 
of  phosphorus  pentachloride  were  heated  on  the  steam-bath 
until  the  action  was  complete.  The  phosphorus  oxychloride 
was  removed  by  heating  in  an  oil-bath  at  140°,  under  a  pres- 
sure of  12  mm.,  for  about  fifteen  minutes.  The  crude  oil  thus 
obtained  weighed  6.5  grams,  a  yield  of  92  per  cent  of  the  cal- 
culated. In  another  preparation  15.5  grams  of  the  2-ethyl- 
mercapto-6-oxypyrimidine  gave  15.5  grams  of  chlorine  com- 
pound, or  90  per  cent  of  the  calculated. 

N=:C— NH2 

2-Ethylmercaplo-6-aminopyrimidint,  C2H6SC          CH        . — 

II  II 

N CH 

When  2-ethylmercapto-6-chlorpyrimidine  (6.5  grams)  was 
heated  in  a  closed  tube  with  alcoholic  ammonia  at  140°  to 
150°,  for  six  hours,  the  action  was  complete.  An  odor  of 
mercaptan  was  apparent  on  opening  the  tube,  showing  too 
energetic  treatment,  and  ammonium  chloride  had  separated. 
The  alcohol  was  removed  by  evaporation,  after  filtering  from 
ammonium  chloride,  and  the  dark  varnish  which  was  obtained 
was  washed  with  a  few  cubic  centimeters  of  cold  water.  By 
this  treatment  the  material  completely  solidified  to  a  hard 


498  Wheeler  and  Johnson. 

cake.  It  was  very  soluble  in  alcohol  and  in  benzene,  and 
fairly  soluble  in  hot  water.  The  weight  of  the  crude  product 
was  4.7  grams,  a  yield  of  82  per  cent  of  the  calculated.  The 
base  dissolved  immediately  in  dilute  hydrochloric  acid  and 
was  precipitated  by  ammonia  in  stout  tables.  It  was  purified 
by  boiling  in  alcohol  with  animal  charcoal  and  then  crystal- 
lizing from  50  per  cent  alcohol.  It  separated  in  the  form  of 
colorless  plates  and  melted  at  85°  to  86°.  A  nitrogen  deter- 
mination gave  :  ' 

Calculated  for 

C6H9N8S.  Found. 

N  27.1  27.6 

In  another  preparation  the  chlorpyrimidine  was  heated 
with  alcoholic  ammonia  at  115°  to  120°  for  five  and  a 
half  hours.  From  15.5  grams  of  the  chlorine  compound  n.6 
grams  of  the  base  were  obtained,  which  is  a  yield  of  84  per 
cent  of  the  calculated. 

NzmzC— NH2 

Cytosincor2-Oxy-6-aminopyrimidine,  CO       CH          .H2O. — 

I  II 

NH  — CH 

The  above  2-ethylmercapto-6-aminopyrimidine  (3  grams)  was 
boiled  with  hydrobromic  acid  of  boiling-point  125°  (i5cc.)  for 
two  hours,  when  mercaptan  had  ceased  being  evolved.  Qn 
evaporating  the  free  hydrobromic  acid  on  the  steam-bath  a 
beautiful  crystalline  mass  of  the  hydrobromide  was  obtained. 
It  crystallizes  in  the  form  of  glistening  prisms  from  a  little  water. 
The  free  base  was  obtained  by  dissolving  the  hydrobromide  in 
water  and  precipitating  with  ammonia.  The  weight  of  the 
crude  base  was  1.9  grams,  which  is  a  yield  of  79  per  cent  of 
the  calculated.  In  another  experiment  7.5  grams  of  2-ethyl- 
mercapto-6-aminopyrimidine  gave  5.6  grams  of  2-oxy-6- 
aminopyrimidine,  or  90  per  cent  of  the  calculated.  The  base 
for  analysis  was  boiled  with  animal  charcoal  and  crystallized 
from  water.  It  was  dried  in  the  air  and  the  water  of  crystal- 
lization determined  by  heating  in  an  oven  at  100°  to  1 10°. 
0.5166  gram  substance  lost  0.0727  gram  on  heating. 


Syntheses  of  Aminooxypyrimidines.  499 

Calculated  for 

C4H6ON8.H,O.  Found. 

H3O  13.95  14-07 

The  analysis  of  the  dried  material  gave  the  following  re- 
sults : 

0.2188  gram  substance  gave  0.3498  gram  CO2  and  0.0835 
gram  H2O. 

0.0939  gram  substance  gave  31  cc.  moist  N  at  25°  and  773 
mm.  pressure. 

Calculated  for 

C4H6ON8.  Found. 

C  43-25  43.6o 

4.50  4.25 

N  37.84  37.72 

Properties  of  2-Oxy-6-aminopyrimidine. — The  free  base, 
when  first  obtained,  crystallized  from  hot  water  in  the  form  of 
needle-like  prisms.  It  was  then  somewhat  colored  (pale 
brownish),  and  melted,  or  rather  decomposed,  at  320°  to  325° 
with  violent  effervescence,  first  becoming  dark-colored  a  little 
below  300°.  After  boiling  in  aqueous  solution  with  animal 
charcoal  it  crystallized  in  the  form  of  beautiful,  colorless, 
transparent  plates.  Ttie  edge  of  one  of  these  crystals,  which 
perhaps  was  made  up  of  a  number  of  plates,  measured  three- 
quarters  of  an  inch  in  length.  The  faces  were  so  badly 
etched,  or  striated,  or  covered  with  vicinal  growths,  that  crys- 
tallographic  measurements  were  impossible.  They  probably 
belong  to  the  mono-  or  tr iclinic  system .  The  plates  had  the  same 
effervescing-point  on  heating  as  the  needle-like  prisms.  These 
decomposing-points  were  taken  in  capillary  tubes,  in  a  paraffin- 
bath,  on  an  Anschiitz  thermometer  13.5  centimeters  in  length, 
and  are  uncorrected.  The  plates  dissolve  in  about  129  parts 
of  water  at  25°.  The  base  is  precipitated  by  phosphotungstic 
acid.  It  would,  therefore,  be  found  in  the  histidine  fraction. 
When  the  acidified  solution  is  treated  with  potassium  bismuth 
iodide  it  gives  a  brick-red  precipitate.  It  gives  the  murexide 
reaction.  With  sulphuric  and  hydrochloric  acids  it  gives 
readily  soluble  salts.  The  chloroplatinate,  and  espe- 
cially the  picrate,  are  difficultly  soluble  in  water.  The  gold 
double  salt  is  also  not  very  soluble.  Kossel  and  Steudel  give 


500  Wheeler  and  fohnson. 

no  melting-  or  decomposing-point  for  their  cytosine,  but  state 
that  the  picrate  turned  brown  on  heating  to  255°  and  melted 
at  270°  with  decomposition. 

2-Oxy-6-aminopyrimidine  Picrate.  —  Picric  acid  produced  an 
immediate  precipitate,  which  crystallized  in  bright-yellow 
needles  or  very  slender,  needle-  like  prisms.  When  made  from 
material  that  had  not  been  decolorized  with  animal  charcoal, 
and  therefore  containing  a  slight  impurity,  it  decomposed 
with  violent  effervescence  quite  sharply  at  about  264°.  When 
prepared  from  the  pure  oxyaminopyrimidine  the  crystals  had 
a  more  pronounced  prismatic  habit  and  they  showed  no  melt- 
ing-point, but  sintered,  became  black,  and  decomposed  at 
about  300°  to  305°.  One  hundred  parts  of  water  dissolve  0.076 
parts  of  the  salt  at  25°.  Our  experience  with  these  picrates 
has  shown  that  the  melting-points  are  rather  indefinite.  They 
can  be  made  to  effervesce  at  a  somewhat  higher  or  lower  tem- 
perature, according  to  the  rate  of  heating.  They  are  difficult 
to  analyze  on  account  of  the  ease  with  which  oxides  of  nitro- 
gen pass  over.  A  nitrogen  determination  of  a  sample  pre- 
pared from  the  pure  base,  for  example,  gave  : 

Calculated  for 
C4H6ON3.C6Hj(N02)8OH.  Found. 

N  24.7  26.4 

The  chloroplatinate  separates  as  a  precipitate  in  yellow 
flakes.  A  platinum  determination  gave  : 

Calculated  for 

Found. 


Pt  30.83  30.60 

2-Oxy-6-acetaminopyrimidine  was  prepared  by  heating  0.5 
gram  of  the  amino  derivative  with  acetic  anhydride.  It 
proved  to  be  practically  insoluble  in  alcohol  and  difficultly 
soluble  in  water.  It  crystallized  from  hot  water  in  colorless, 
microscopic  prisms,  with  rough  faces,  frequently  occurring  in 
crosses.  It  showed  no  signs  of  melting  at  300°.  A  nitrogen 
determination  gave  : 

Calculated  for 
C8H7O8N8.  Found. 

N  27.44  27.82 


Syntheses  of  Aminooxypyrimidines.  501 

The  phenyl  isocyanate  derivative  was  prepared  by  heating 
0.5  gram  of  the  base  with  0.55  gram  of  phenylisocyanate  on 
the  steam-bath  for  six  hours.  The  white  crystalline  product 
which  resulted  proved  to  be  very  insoluble.  It  was  boiled  re- 
peatedly with  alcohol  and  then  digested  with  water.  The  in- 
soluble material  thus  obtained  began  to  sinter  on  heating  at 
about  255°,  and  then  melted  with  violent  effervescence  at  260°. 
A  nitrogen  determination  agreed  with  the  calculated  for  an  ad- 
dition of  2  molecules  of  phenyl  isocyanate  to  one  of  the  base. 

Calculated  for 
(i  :  i)  (2  :  i) 

CnHioOjN*.  Ci8Hi508N5.  Found. 

N  24.34  20.05  20.4 

Action  of  Bromine. — Three-tenths  gram  of  2-oxy-6-amino- 
pyrimidine  was  treated  with  i  gram  of  glacial  acetic  acid,  and 
0.5  gram  of  bromine  was  added.  An  immediate  reaction  took 
place,  heat  was  evolved,  and  an  orange  powder  separated, 
which  dissolved  on  warming.  Some  water  was  added  to  the 
cooled  solution  and  the  precipitate  produced  was  crystallized 
from  water.  It  formed  well-crystallized,  colorless  needles, 
and  it  melted  sharply  at  247°  with  effervescence.  When  dis- 
solved in  water  and  made  alkaline  with  ammonia  it  gave  a 
strong,  wine-red  color,  and,  on  cooling,  a  brick-red  substance 
separated.  This  had  no  definite  melting-point. 

NH— CO 

2-Amino-6-oxypyrimidine,  H,N — C         CH. — Thirty  grams 

II          II 
N CH 

of  guanidine  carbonate  were  dissolved  in  100  cc.  of  water  and 
mixed  with  54  grams  of  crystallized  barium  hydrate  in  400  cc. 
of  water.  The  solution  was  filtered  and  55  grams  of  sodium 
ethyl  formylacetate  were  added.  The  whole  dissolved  except 
a  slight  sediment.  After  standing  for  three  hours  the  solu- 
tion was  divided  into  two  equal  portions.  One  was  allowed 
to  stand  over  night,  the  other  was  warmed  on  the  steam-bath 
for  a  few  minutes,  and  then  just  acidified  with  sulphuric  acid. 
The  filtered  solution  on  evaporation,  and  adding  ammonia 
in  excess,  gave  a  crystalline,  brown  precipitate,  weigh- 


502  Wheeler  and  Johnson. 

ing  6.7  grams,  or  36  per  cent  of  the  calculated.  The  portion 
that  stood  over  night,  on  similar  treatment,  gave  practically 
the  same  yield,  so  that  long  standing  does  not  better  the 
yield.  In  another  experiment  10  grams  of  guanidine  carbon- 
ate and  22  grams  of  sodium  ethyl  formylacetate  gave  4.8 
grams  of  the  base,  which  is  a  yield  of  39  per  cent  of  the  cal- 
culated. On  boiling  the  crude  products  with  animal  char- 
coal, in  aqueous  solution,  the  color  is  slowly  removed  and,  on 
cooling,  small,  flat,  colorless,  transparent  prisms  generally 
separate.  These  crystals,  when  air-dried,  contained  less  than 
0.5  per  cent  of  water.  A  nitrogen  determination  (I.)  gave  : 

I.  0.0900  gram  substance  gave  30.6  cc.  of  moist  N  at  26°. 5 
and  762  mm.  pressure. 

II.  0.1357  gram  substance  gave  44.8  cc.  of  moist  N  at  24° 
and  768  mm.  pressure. 

Calculated  for  Found. 

C4H5ON3.  I.  II. 

N  37-83  37.98  37-45 

In  another  experiment,  as  above,  the  base  was  crystallized 
from  water,  purified  with  animal  charcoal,  and  when  a  por- 
tion had  separated  from  the  still  warm  solution,  in  the  form  of 
prisms,  the  mother- liquor  was  decanted.  It  then  became  al- 
most semi-solid  from  the  separation  of  a  mass  of  long,  slender, 
colorless,  silky  needles  which,  on  drying  in  the  air,  formed  a 
bulky,  felt-like  mass.  This  material  contained,  or  occluded, 
water,  but  the  determinations  were  not  constant :  0.8567  gram 
substance  lost  0.1036  gram  on  heating  to  100°  to  110°,  equiva- 
lent to  12.0  per  cent  water.  The  needle  form  appears  to  re- 
sult also  from  dilute  solutions  or  on  rapidly  cooling.  2.0527 
grams  of  substance  prepared  in  this  manner,  on  standing  in 
the  air  for  eight  or  nine  hours  and  then  heating,  lost  0.1657 
gram,  equal  to  8.7  per  cent  of  water.  The  calculated  for  i 
molecule  of  water  is  13.9  per  cent.  A  nitrogen  determination 
of  the  dried  material  is  given  above  (Analysis  II.). 

Properties  of  2-Amino-6-oxypyrimidine. — It  was  found  that 
the  needles  gave  the  stout  prisms  and  the  prisms  could  be  ob- 
tained in  needle  form  under  slight  changes  in  the  crystalliza- 
tion. The  crystals  were  not  suitable  for  crystallographic 


Syntheses  of  A minooxypyrimidincs,  503 

measurements,  the  faces  being  highly  etched,  especially  the 
end  faces  of  the  prisms.  The  material  melts,  or  rather  de- 
composes, with  violent  effervescence,  at  about  276°.  This 
effervescing-point  may  vary  several  degrees,  according  to  the 
rate  of  heating. 

The  base  is  precipitated  by  phosphotungstic  acid.  It  is  not 
precipitated  by  potassium  bismuth  iodide  in  hydrochloric  acid 
solution,  but  it  gives  a  brick-red  precipitate  in  solutions  of 
the  base  in  sulphuric  acid.  It  gives  the  murexide  reaction. 
Its  sulphate  and  hydrochloride  are  readily  soluble  in  water 
and  the  former  crystallizes  in  flat  prisms.  The  picrate  is  very 
difficultly  soluble  and  the  gold  and  platinum  double  salts  are 
also  not  very  soluble.  When  heated  with  20  per  cent  sul- 
phuric acid  for  two  hours,  at  145°  to  150°,  a  portion  of  the  ma- 
terial is  converted  into  uracil. 

2-Amino-6-oxypyrimidine  Picrate. — When  picric  acid  is 
added  to  a  hot  solution  of  the  base  in  water  a  mass  of  bright- 
yellow  needles  separate.  If  slowly  cooled  slender  prisms  are 
formed.  On  heating,  the  crystals  become  less  transparent  at 
about  1 80°,  showing  evidence  of  darkening  at  about  255°,  and 
signs  of  melting  at  270°.  Between  this  point  and  280°  they 
generally  effervesce.  They  dissolve  in  about  1200  to  1300 
parts  of  water  at  25°.  A  nitrogen  determination  gave  : 

Calculated  for 
C4H6ON3.C8H2(N02)30H.  Found. 

N  24.70  24.72 

The  chloroplatinate  separates  in  the  form  'of  small  yellow 
needles,  which  form  acicular  crystals  or  spikes  on  slowly 
cooling  the  hot  solutions.  On  heating,  it  decomposes  above 
200°,  becoming  brown,  but  not  melting  below  286°.  A 
platinum  determination  gave  : 

Calculated  for 
(C4H60N3)2H2PtCl6.  Found. 

Pt(=i94.8)  30.83  30.56 

The  gold  chloride  double  salt,  which  seems  to  be  more  solu- 
ble than  the  platinum  double  salt,  forms  bright-yellow,  stout 
prisms,  which  easily  form  a  supersaturated  solution.  A  gold 
determination  gave : 


504  Wheeler  and  Johnson. 

Calculated  for 
C4H6ON8.HCl.AuCl3.  Found. 

Au(=i95.7)  43-51  43-57 

2-Acetamino-6-oxypyrimidine. — One-half  gram  of  the  base 
required  about  7.5  grams  of  boiling  acetic  anhydride  to  effect 
solution.  On  cooling,  a  colorless  mass  of  crystals  separated,  so 
bulky  that  the  test-tube  could  be  inverted  without  loss  of  the 
contents.  This  material  crystallizes  in  bunches  of  minute 
mother-of-pearl  scales  from  alcohol,  and  it  melts  at  247°  to  a 
clear  liquid.  A  nitrogen  determination  gave  : 

Calculated  for 
C6H7O2N3.  Found. 

N  27.45  27.69 

2-Amino-5-brom-6-oxypyrimidine. — Three  grams  of  the  base 
were  suspended  in  20  cc.  of  glacial  acetic  acid,  in  which  it  is 
difficultly  soluble,  and  4.5  grams  of  bromine  were  dropped  in. 
The  action  took  place  smoothly  and  an  orange  powder  sepa- 
rated. It  weighed  6.6  grams,  while  the  calculated  amount 
for  a  hydrobromide  of  2-amino-5-brom-6-oxypyrimidine  is  7.2 
grams.  The  yield  obtained  was  83  per  cent  of  the  theoretical. 
This  hydrobromic  acid  salt  forms  long,  slender,  needle-like 
prisms,  when  crystallized  from  water,  and  it  melts  at  about 
273°  with  strong  effervescence.  When  the  aqueous  solution 
of  this  is  treated  with  ammonia  the  brom-base  separates  as  a 
compact,  granular  precipitate,  insoluble  in  alcohol  and  ex- 
tremely difficultly  soluble  in  water.  It  crystallizes  from 
strong  acetic  acid  in  radiating  masses  of  pointed  plates,  and 
it  melts  with  decomposition  at  about  the  same  temperature  as 
the  hydrobromide  or  the  bromine-free  base.  It  has  acid 
properties  and  it  dissolves  in  strong  ammonia,  but  separates 
again  unaltered  on  boiling  off  the  ammonia.  A  nitrogen  de- 
termination gave  : 

/  .     Calculated  for 

C4H4ON3Br.  Found. 

N  22.10  22.13 

NEW  HAVEN,  CONN.,  March  20,  1903. 


I  Reprinted  from  the  American  Chemical  Journal,  Vol.  XXIX.    No.  5. 
May,  1903.1 


Contributions  from  the  Sheffield  Laboratory  of  Yale  University. 

Civ.— ON    CYTOSINE    OR     2-OXY-6-AMINOPYRIMI- 
DINE  FROM  TRITICO-NUCLEIC  ACID. 

BY  HENRY  L.  WHEELER  AND  TREAT  B.  JOHNSON. 

It  has  been  shown  by  Osborne  and  Harris1  that  uracil  can 
be  obtained  from  the  nucleic  acid  of  the  wheat  embryo.2  As 
we  wished  to  compare  our  synthetic  uracil  with  some  of  the 
natural  we  asked  Dr.  Osborne  for  a  sample.  Not  having  the 
pure  substance  at  hand,  he  very  kindly  supplied  us  with  1.35 
grams  of  material  obtained  by  evaporating  the  mother-liquors 
from  the  crystallization  of  his  uracil. 

We  found  that  the  material,  after  crystallizing  six  times 
from  water,  gave  a  solution  which,  on  slowly  evaporating,  de- 
posited flat,  needle-like  crystals,  about  a  centimeter  in  length. 
This  material  was  obviously  not  uracil,  and,  at  Dr.  Osborne' s 
suggestion,  we  then  examined  the  material  for  cytosine.  We 
found,  in  fact,  that  it  consisted  of  a  mixture  of  apparently 
about  equal  parts  of  uracil  and  cytosine. 

When  a  solution  of  3  grams  of  picric  acid,  dissolved  in  200 
cc.  of  hot  water,  was  added  to  the  1.35  grams  of  material  dis- 
solved in  50  cc.  of  hot  water  and  the  mixture  was  allowed  to 
stand  for  twelve  hours,  beautiful,  long,  silky,  bright-yellow 
needles  separated.  The  weight  of  the  picrate  obtained  was 
1.7  grams.  The  needles,  which  had  every  appearance  of 
purity,  melted  with  effervescence,  as  Kossel  and  Steudel3  state 
in  the  case  of  thymus  cytosine  at  about  270°,  turning  brown  a 
number  of  degrees  below  this  temperature.4  We  took  exactly 
i  gram  of  this  picrate  for  the  preparation  of  the  free  base. 
The  picrate  was  treated  with  an  excess  of  sulphuric  acid  and 

1  Ztschr.  physiol.  Chem.,  36,  85  ;  Annual  Report  for  1901  of  the  Connecticut  Agri- 
cultural Experiment  Station,  page  408. 

Osborne  and  Campbell :  J.  Am.  Chem.  Soc.,  22,  379. 

*  Ztschr.  physiol.  Chem.,  37,  378  (1903). 

*  Owing  to  the  ease  with  which  this  picrate  gives  off  oxides  of  nitrogen,  the  analyt- 
ical results  came  high  both  for  carbon  and  nitrogen,  so  that  the  results   were  with- 
out value.    In  this  connection  it  may  be  stated  that  a  jnitrogen  determination  gave 
36.5  per  cent  nitrogen,  while  a  precisely  similar  result  was  obtained  in  the  case  of 
the  picrate  from  the  synthetic  base,  namely  26.4  per  cent  nitrogen.    The  calculated 
for  C4H6ON8.CcHa(NOa)8OH  is  24.7  per  cent  nitrogen. 


506  Wheeler  and  Johnson . 

the  picric  acid  was  removed  by  shaking  with  ether.  The 
sulphuric  acid  was  mostly  removed  by  barium  hydrate,  and, 
on  concentrating  and  adding  ammonia,  colorless,  well-crys- 
tallized, slender,  needle-like  prisms  of  the  free  base  separated. 
The  amount  of  this  material  was  0.1641  gram.  This,  after 
washing  with  water,  was  dried  by  standing  in  the  air,  on 
paper,  for  twelve  hours.  It  then  lost  0.0181  gram  on  heating 
to  constant  weight  at  110°  to  120°,  equivalent  to  11.30  per  cent 
of  water,  while  the  calculated  for  C4H5ON3.H2O  is  13.9  per 
cent  water. 

This  base  melted  with  strong  effervescence  at  about  323°, 
precisely  like  the  synthetical  2-oxy-6-arninopyrimidine,  and 
when  a  portion  was  mixed  with  the  latter  substance  the  melt- 
ing- or  effervescing-point  was  not  lowered. 

After  determining  the  solubility  in  water  (see  below)  the 
base  was  then  converted  into  the  chloroplatinate.  A  platinum 
determination  gave : 

0.0830  gram  substance  gave  0.0253  gram  platinum. 

Calculated  for 
(C4H5ON8)2H2PtCl6.  Found. 

Pt(=i94.8)  30.83  30.48 

The  remaining  material  was  given  to  Professor  S.  L.  Penfield 
for  a  crystallographic  examination  and  comparison  with  the 
corresponding  platinum  double  salt  prepared  from  2-oxy-6- 
aminopyrimidine.  Kossel  and  Steudel1  state,  in  regard  to 
the  platinum  chloride  double  salts  prepared  by  them,  that 
11  Das  Platindoppelsalz  des  Storcytosins  zeigte  namlich  fast 
durchweg  doppelbrechende  Zwillingsformen,  welche  in  der 
Weise  aneinander  gelagert  waren,dass  die  Ausloschungsrich- 
tung  in  dem  einen  Krystall  einen  Winkel  von  53°  mit  der 
Ausloschungsrichtung  des  anderen  Krystalls  bildete.  Diese 
Winkel  wurden  beim  Cytosin  aus  Herings-und  Stb'rtestikeln 
gleich  befunden,  beim  Cytosin  aus  Thymusnucleinsaure 
haben  wir  bisher  solche  Zwillingsformen  uberhaupt  tiicht 
beobachtet." 

1  Ztschr.  physiol.  Chem.,  37,  379  (1903)- 


Cytosine,  Etc.^Jrom  Tritico- Nucleic  Acid. 


507 


Crystallography  of  2~Oxy~6-aminopyrimidine  Chloroplatinate 
{Synthetic  Cytosine  Chloroplatinate}. 

The  crystals  submitted  for  study  were  thin  plates  and  for 
examination  with  the  microscope  they  were  embedded  in  oil, 
and  over  them  a  cover  glass  was  placed. 


Fig.  I.  Fig.  II.  Fig.  III. 

Figure  I.  represents  the  habit  of  one  of  the  crystals  which 
was  unbroken  and  of  almost  ideal  symmetry.  It  is  a  twin, 
presumably  belonging  to  the  monoclinic  system,  the  large  flat 
face  b  being  the  clinopinacoid  (oio).  The  edges  c,  a,  and  e 
appear  as  sharp  lines  under  the  microscope,  and  represent  the 
direction  of  faces  at  right  angles  to  b\  It  may  be  assumed 
that  c  is  the  base  (ooi)  and  a  the  orthopinacoid  (100),  the  in- 
clination of  the  axes,  ft,  being  about  60°.  Some  beveling 
form,  5,  appears  at  the  upper  corners,  which  may  be  taken  as 

the  monoclinic  pyramid  (T 1 1 ) ,  its  intersection  with  b  making 
an  angle  of  about  41°  with  the  vertical  axis  (the  trace  of  a), 
as  indicated  in  the  figure.  The  faces  e  at  the  top  are  ortho- 
domes,  inclined  about  75°  to  the  vertical  axis,  and  they  have 

the  symbol  (Io2).  The  twinning  plane,  uniting  the  two  in- 
dividuals, is  the  orthopinacoid  a.  The  extinction,  indicated 
in  the  figure  by  the  arrows,  is  inclined  about  2°. 5  either  side 
of  the  twinning  plane. 

A  second  crystal,  Fig.  II.,  was  like  the  one  just  described, 
except  for  the  faces  d  at  the  top,  which  make  an  angle  of 
about  91°  with  the  vertical  axis.  The  form  d  is  evidently  an 

orthodome,  and  has  the  symbol  (103). 

A  third  crystal,  Fig.  III.,  showed  two  kinds  of  twinning. 
Crystals  I.  and  II.  are  twinned  about  the  orthopinacoid  as  in 


508 


Wheeler  and  Johnson . 


Fig.  I.,  while  II.  and  III.  have  the  base  c  as  the  twinning 
plane.  The  extinction  is  indicated  by  the  arrows.  In  crys- 
tals II.  and  III.  the  extinction  directions  make  an  angle  of 
55°  with  one  another. 

Crystallography  of  Wheat  Cytosine  Chloroplatinate . 

The  crystals  submitted  for  study  were  much  thinner  than 
those  prepared  from  synthetic  cytosine,  hence  when  mounted 
in  oil  for  examination  they  were  much  more  broken. 


Fig.  IV.  Fig.  V.  Fig.  VI. 

Fig.  IV.  represents  a  fragment  of  a  twin  crystal,  the  part 
to  the  right  of  the  twinning  plane  not  being  shown.  The  ar- 
rangement of  the  faces  and  the  angles  is  like  Fig.  II.,  except 
/",  at  the  top,  which  makes  an  angle  of  106°  with  the  vertical 

axis  and  corresponds  to  an  orthodome   (106). 

Fig.  V.  represents  a  part  of  another  twin  crystal,  like  Fig. 
IV.,  except  that/ and  c  terminate  the  crystal  instead  of  d  and 
/.  The  extinction  was  2°.  5  from  the  vertical  axis  as  in  the 
case  of  the  synthetic  preparation. 

Among  the  broken  fragments  two  kinds  of  twinning  were 
observed,  some  with  a  as  the  twinning  plane  and  others  like 
Fig.  VI.,  with  the  base  c  as  the  twinning  plane.  In  the  latter 
the  twinning  law  is  the  same  as  that  of  crystals  II.  and  III.  of 
Fig.  III.  The  extinction  is  nearly  parallel  to  «,  and  makes 
an  angle  with  the  twinning  plane  of  62°. 5,  or  the  two  extinc- 
tion directions  make  an  angle  of  55°  with  one  another. 

Aside  from  the  extinction  directions  the  optical  properties 
of  the  crystals  were  not  very  decisive.  When  examined  in 
convergent  light  an  indistinct  interference  figure  was  seen, 
presumably  the  center  of  the  cross  of  an  obtuse  bisectrix. 


Cytosien,  Etc. ,  from  Tritico- Nucleic  Arid. 


509 


The  identity  of  the  synthetic  cytosine  and  wheat  cytosine  is 
established  beyond  question  by  the  crystallographic  similarity 
of  the  two  chloroplatinates. 

The  measurements  given  were  made  under  the  microscope, 
and  only  approximate  accuracy  is  claimed  for  them.  The 

symbols  of  the  domes  e  (102),  d  (103),  and/  (106)  were  de- 
termined by  plotting. 

Dr.  P.  A.  Levene  has  very  kindly  sent  us  a  pure  sam- 
ple of  his  base  from  the  spleen  which  has  the  properties 
and  composition  of  Kossel  and  Steudel's  cytosine.  The 
amount  of  this  at  our  disposal  was  about  0.12  gram.  It 
formed  thin,  flat,  colorless  crystals  or  prismatic  plates,  and  it 
melted  or  effervesced,  side  by  side  with  the  synthetic  material 
at  323°,  and,  when  portions  of  these  substances  were  mixed, 
the  melting-point  was  not  altered  in  the  slightest.  After  de- 
termining the  solubility  we  converted  this  material  into  the 
chloroplatinate.  Professor  Penfield  then  reported  on  the  crys- 
tallography as  follows  : 

Crystallography  of  Spleen  Cytosine  Chloroplatinate. 

The  crystals  are  like  the  ones  previously  described,  having 
the  same  angles,  though  presenting  some  variation  in  habit. 
Fig.  VII.  is  typical,  showing  a,  b,  c,  and  s  forms,  but  with 


Fig.  IX. 


5 1  o  Wheeler  and  Johnson . 

the  reentrant  angle  at  the  top  having  a  curved  contour  so  that 
no  definite  symbol  can  be  assigned.  The  extinction,  as  in 
the  other  preparations,  is  2°. 5  either  side  of  the  twinning 
plane,  as  indicated  by  the  arrows  in  the  figure. 

Fig.  VIII.  represents  a  penetration  twin,  drawn  with  camera 
lucida.  The  two  opposite  parts  I.  and  I.  extinguish  simul- 
taneously, as  also  II.  and  II.  Many  crystals  of  the  crop  sub- 
mitted for  examination  were  long,  lath-shaped  individuals, 
Fig.  IX.  Several  having  this  habit  were  twinned  about  the*: 
face. 

The  three  chloroplatinates  prepared  from  synthetic  cytosine, 
wheat  cytosine,  and  spleen  cytosine  are  crystallographically 
identical  and  show  no  greater  variation  in  habit  than  is  gen- 
erally observed  on  crystals  of  any  substance  formed  under 
varying  conditions. 

The  solubility  of  the  three  samples  of  cytosine  in  water  at 
25°  was  determined  with  the  following  results  : 

loo  parts  water  dissolve  0.83  part  wheat  cytosine. 

100  parts  water  dissolve  0.78  part  spleen  cytosine. 

loo  parts  water  dissolve  0.79  part  synthetic  cytosine. 

The  high  result  in  the  case  of  wheat  cytosine  is  probably 
due  to  the  fact  that  it  was  not  as  pure  as  the  others.  Owing 
to  lack  of  material  the  determination  was  made  with  the 
above-mentioned  sample,  which  had  been  washed  but  not  re- 
crystallized  from  water. 

We  conclude,  from  these  results,  that  the  products  obtained 
from  the  three  different  sources  are  identical,  and  that  cyto- 
sine, is  as  Kossel  and  Steudel  have  predicted,  an  oxyamino- 
pyrimidine,  viz.,  2-oxy-6-aminopyrimidine.  Its  structure  is 
to  be  represented  by  the  following  formula,  or  a  tautomeric 
form : 

N=rC— NH2 

OC         CH         .H2O. 

I  II 

HN CH 

Hitherto  cytosine  has  been  found  only  in  animal  organs. 
The  present  results  offer  further  evidence  of  the  similarity  of 
nucleic  acids  of  animal  and  vegetable  origin. 


Cytosine,  Etc. ,  from  Tritico- Nucleic  Add.  511 

We  take  pleasure  in  thanking  Dr.  Osborne  and  Dr.  I,evene 
for  the  material  placed  at  our  disposal  and  Professor  Penfield 
for  the  crystallographic  descriptions. 

NEW  HAVEN,  CONN.,  March  25,  1903. 


L  Reprinted  from  the  American  Chemical  Journal,  Vol.  XXXI,  No.  6. 
June,  1904.] 


Contributions  from  the  She  meld  Laboratory  of  Yale  University. 

CXVI.— RESEARCHES    ON    PYRIMIDINE    DERIVA- 
TIVES :    5-METHYLCYTOSINE. 
[FIFTH  PAPER.] 

BY  HENRY  I*.  WHEELER  AND  TREAT  B.  JOHNSON. 

In  a  previous  paper  we1  showed  that  cytosine  gives  uracil 
on  heating  with  acids.     If  uracil  is  to  be  reckoned  as  cytosine 
in  the  nucleic  acids  then  5-methyluracil  or  thymine  possibly 
results  by  the  cleavage  of  a   corresponding  base,    namely,        , 
5-methylcytosine    (formula    I.)    or  tfre   isomeric   2-amino-5-  r 
methyl- 6-oxypyrimidine  (III.)  :      / 

N=C— NH,  HN— CO  HN— CO 

I         1,-N     -  II  II 

OC     CQH/        -~     OC     CCH,    —    H,N— C     CCHS 

I      II  I      II  II      II 

HN— CH  HN— CH  N— CH 

I.  II.  III. 

We  therefore  decided  to  prepare  these  new  bases  and  to 
compare  their  properties  with  those  of  cytosine.  In  this  paper 
we  describe  5-methylcytosine  and  in  a  later  paper  by  Dr. 
Johnson  and  Mr.  S.  H.  Clapp,  the  compound  represented  by 
formula  III.  will  be  discussed.  We  prepared  the  compound 
represented  by  formula  I.  as  follows  :  The  ethyl  bromide  ad- 
dition-product of  thiourea  was  treated  with  one  molecular 

1  This  JOURNAL,  29,  494  (1903). 


592  Wheeler  and  Johnson. 

proportion  of  alkali  in  aqueous  solution  and  the  sodium  salt 
of  ethyl  formylpropionate  added.  On  standing,  then  warm- 
ing for  a  few  minutes,  cooling,  and  acidifying  with  acetic 
acid,  2-ethylmercapto-5-tnethyl-6-oxypyrimidine  was  obtained. 

NH2       C2H5OCO  NH— CO  C2H5OH 

I  I  II 

C2H5SC       +  CCH3  =  C2H5SC         CCH3  + 

II  II  II          II 

NH  NaOCH  N CH  NaOH 

The  2-ethylmercapto-5-methyl-6-oxypyrimidine  was  con- 
verted into  2-ethylmercapto-5-methyl-6-chlorpyrimidine  by 
means  of  phosphorus  pentachloride  : 

NH— CO  N=CC1 

II  II 

C2H5SC         CCH3  +  PC15  =  C2H5SC     CCH3  +  POC13. 

II          li  II      I          +  HC1 

N CH  N— CH 

When  2-ethylmercapto-5-methyl-6-chlorpyrimidine  was 
heated  with  strong^a,lcgholic_ammonia  it  gave  2-ethylmercap- 
to-5-methyl-6-aminopyrimidine. 

—  ppl  xr — p TSTTT 

— —  v^^i  i>  —  v^^J-N  -C19 

II  II 

C2H5SC     CCH3  +  2NH3  =  C2H6SC     CCH8      +  NH4C1. 

II      II  II      II 

N— CH  N— CH 

Finally  the  2-ethylmercapto-5-methyl-6-aminopyrimidine  was 
converted  into  the  halogen  hydride  salt  of  2-oxy-5-methyl-6- 
aminopyrimidine  by  boiling  with  either  Jiydrochloric  or  hy- 


N=C— NH2  N=C— NH2,HX 

II  II 

C2H5SC     CCH3      +  H2O  =  OC     CCH8  +  C2H5SH. 

II      II  I      II 

N— CH  HN— CH 

5-Methylcytosine  separates  from  water  with  a  half  molecule 
of  water  of  crystallization  while  cytosine  crystallizes  with  i 
molecule  of  water. 


5-Methykyiosinc.  593 

5-Methylcytosine  is  about  five  times  as  soluble  in  water  as 
cytosine  and  ten  or  eleven  times  as  soluble  as  thymine  or 
uracil  and  it  is  readily  decomposed  into  thymine  by  20  per 
cent  sulphuric  acid  at  150°.  It  is  probable  that  in  the  decom- 
position of  the  nucleic  acids  by  the  prolonged  action  of  hot 
acids  this  base  would,  if  present,  be  converted  entirely  into 
thymine. 

One  of  the  most  characteristic  properties  of  5-methylcyto- 
sine  is  its  tendency  to  form  the  so-called  abnormal  or  basic  2  :  i 
salts  with  hydrochloric  and  hydrobromic  acids.  When  am- 
monia in  excess  is  added  to  a  solution  of  cytosine  in  these 
acids,  free  cytosine  usually  separates.  In  the  case  of  5-methyl- 
cytosine  in  the  halogen  hydride  acids  the  precipitate  gener- 
ally consists  of  the  salt  (C6H7ONS)2HX.H2O. 

Cytosine  gives  a  i  :  2  salt  with  concentrated  hydrochloric 
acid ;  5-methylcytosine  gives  a  i  :  i  salt  under  the  same  con- 
ditions. 

The  picrate  of  5-methylcytosine,  which  forms  yellow,  long, 
slender,  needle-like  prisms,  has  the  same  solubility  in  water 
as  cytosine  picrate. 

5-Methylcytosine  is  precipitated  by  phosphotungstic  acid  ; 
it  therefore  differs  from  the  new  base  prepared  by  Kutscher1 
from  thymus  nucleic  acid. 

An  attempt  was  made  to  prepare  2-oxy-5,6-diaminopyrimi- 
dine  by  brominating  2-ethylmercapto-6-oxypyrimidine2  (IV.), 
chlorinating  in  the  6-position  by  means  of  phosphorus  penta- 
chloride,  and  then  attempting  to  replace  both  of  the  halogens 
by  the  amino  group  in  this  compound  (VI.)  by  means  of  al- 
coholic ammonia  at  a  high  temperature.  It  was  found  that 
the  chlorine  could  be  replaced  by  the  amino  group  with  ease, 
but  that  the  bromine  was  far  more  firmly  bound,  the  compound 
VII.  being  almost  quantitatively  obtained.  This  was  con- 
verted into  5-bromcytosine  (VIII.)  and  this  compound  then 
heated  with  aqueous  ammonia,  but  here  again  the  desired  di- 
amino  derivative  was  not  obtained.  These  results  recall  the 
similar  behavior  of  4-methyl-6-amino-5-brompyrimidine  de- 

1  Ztschr.  physiol.  Chem.,  38,  173  (1903). 

2  Wheeler  and  Merriam  :  This  JOURNAL,  29,  484  (1903). 


594  Wheeler  and  Johnson. 

scribed  by  Gabriel  and  Colman.1    This  substance  did  not  re- 
act with  ammonia  without  complete  decomposition. 

HN— CO  HN— CO  N=CC1 

C3H5SC     CH    •—     C2H5SC     CBr     -—     CaH5SC     CBr. 

II      H  II       II  II      II 

N— CH  N  — CH  N— CH 

IV.  V.  VI. 

N=C— NH,  N=C— NH2        N=C-NHa 

C2H5SC     CBr  -~-     OC     CBr  OC     C— NH2. 

II      II  I      II  |       II 

N— CH  HN— CH  HN— CH 

VII.  VIII.  IX. 

The  action  of  nitric  acid  was  next  tried  on  cytosine,  where- 
upon it  was  found  that  nitration  took  place ;  the  compound 
formed  was  not  a  5-nitro  derivative,  but  rather  the  nitramide 
whose  structure  is,  in  all  probability,  shown  by  formula  X. 

N=C— NHa  N=C— NHNO, 

II  II 

OC     CH  —     OC     CH 

I       II  I       II 

HN— CH  HN— CH 

x. 

The  formation  of  similar  nitramide  derivatives  in  the  pyrimi- 
dine  series  has  been  observed  by  Gabriel  and  Colman.8 

Work  on  the  preparation  of  oxydiaminopyrimidines  will  be 
continued  here.  These  particular  pyrimidine  compounds  are 
of  special  interest  not  only  because  Kutscher8  believes  that 
he  has  isolated  such  a  compound,  in  the  form  of  its  picrate, 
from  yeast,  but  also  on  account  of  the  fact  that  if  an  oxydi- 
aminopyrimidine  is  found  to  crystallize  or  combine  with  3 
molecules  of  water  it  would  then  have  the  same  percentage 
composition  as  Drechsel's  so-called  diaminoacetic  acid*  and 
perhaps  the  substances  would  prove  to  be  identical.  Will- 
statter6  has  shown  that  diaminoacetic  acid,  if  capable  of  ex- 

1  Ber.  d.  chem.  Ges.,  34,  1239  (1901). 

2  Ibid.,  34,  1240-1241  (1901). 

*  Ztschr.  physiol.  Chem.,  38,  176  (1903). 

*  Beilstein  :  Handbuch  I.,  1194. 

6  Ber.  d.  chem.  Ges.,  35,  1378  (1901). 


5-Methylcytosinc.  595 

istence,  would  not  agree  in  properties  with  Drechsel's  com- 
pound. In  other  words,  Drechsel's  compound  might  be  a 
pyrimidine  derivative  as  follows  : 


CHCOOH      =  C4H120,N4  =  C4H6ON4  +  3H2O. 


n 

= 
J 


EXPERIMENTAL  PART. 

2-Ethylmercapto-5-methyl-6-oxypyrimidine, 
HN—  CO 

I  I 

C,H5SC     CCH,.  —  When  a  mixture  of  150  grams  of  ethyl  pro- 

II  II 
HN—  CH 

pionate  and  135  grams  of  ethyl  formate,  in  somewhat  over  2 
volumes  of  dry  ether,  were  slowly  dropped  upon  34  grams  of 
sodium,  about  125  grams  of  crude  sodium  ethylformylpro- 
pionate1  were  obtained.  In  using  this  salt  and  also  sodium 
ethylformyl  acetate  to  condense  with  the  alkyl  halide  addi- 
tion-products of  thiourea  we2  employed  the  substances  in 
molecular  proportions.  It  has  since  been  found  in  both  cases 
that  only  about  one-half,  or  less,  of  the  quantity  of  the  salt 
taken  reacts  in  the  desired  manner,  and  therefore  that  one- 
half  the  calculated  quantity  of  pseudoethylthiourea  hydrobro- 
mide  gives  about  the  same,  if  not  a  better,  yield  of  pyrimidine 
as  when  the  substances  are  used  in  molecular  proportions. 
From  125  grams  of  the  salt  and  150  grams  of  the  ethyl  bro- 
mide addition-product  of  thiourea  we  obtained,  in  the  manner 
already  described,  39.5  grams  of  this  mercaptopyrimidine. 
This  is  28  per  cent  of  the  calculated.  In  another  experiment 
90  grams  of  the  sodium  salt  with  87  grams  of  the  thiourea 
addition-product  gave  20.5  grams  of  the  pyrimidine  deriva- 
tive, or  26  per  cent  of  the  theoretical  amount. 

2-Ethylmercapto-5-methyl-6-oxypyritnidine  crystallizes  from 
hot  water  in  the  form  of  long,  slender  prisms.     It  is  very  sol- 

1  Wislicenus  :  Ber.  d.  chem.  Ges.,  20,  2933  (1887). 

2  This  JOURNAL,  29,  487  ;  Ibid.,  29,  496  (1903). 


596  Wheeler  and  Johnson. 

uble  in  alcohol  and  it  melts  at  158°  to  159°.     A  nitrogen  de- 
termination gave  : 

Calculated  for 
C7H10ON2S.  Found. 

N  16.47  16.78 

2-Ethylmercapto-5-methyl-6-chlorpyrimidine, 


I  I 

C2HSSC      CCH3.  —  Phosphorus     pentachloride     reacts     less 

II  II 
N— CH 

smoothly  with  the  above  mercapto  derivative  than  it  does  with 
2-ethylmercapto-6-oxypyrimidine.  When  the  mixture  of  the 
substances  in  molecular  proportions  is  warmed  on  the  steam- 
bath,  hydrogen  chloride  is  evolved,  and,  on  cooling,  the  ma- 
terial solidifies  to  a  deliquescent,  crystalline  cake.  This  is 
apparently  a  double  compound  of  the  chlorpyrimidine  and 
phosphorus  oxychloride.  If  an  attempt  is  made  to  distil  this 
directly  in  a  vacuum,  decomposition  takes  place  and  the  ma- 
terial turns  black.  If,  however,  the  cake  is  transferred  to 
crushed  ice  it  liquefies,  and  on  shaking  out  with  ether  and 
drying,  the  resulting  oil  can  then  be  distilled  under  dimin- 
ished pressure.  In  one  experiment,  35  grams  of  the  mercapto- 
oxy  derivative  and  43.5  grams  of  phosphorus  pentachloride 
gave  24  grams  of  the  distilled  chloride,  which  is  a  yield  of 
61.8  per  cent  of  the  calculated.  In  another,  20  grams  gave 
14.5  grams  of  the  chloride  or  65  per  cent  of  the  calculated. 

2-Kthylmercapto-5-methyl-6-chlorpyrimidine  boils  at  146° 
to  147°  at  17  mm.  pressure,  and  at  157°  to  159°  at  25  to  26 
mm.  pressure.  It  was  thus  obtained  as  a  colorless,  almost 
odorless,  oil,  which  did  not  solidify  in  a  freezing- mixture. 

2-Ethylmercapto-6-chlorpyrimidine,  prepared  and  purified 
in  a  similar  manner,  was  found  to  boil  at  135°  at  24  mm. 
pressure. 

A  nitrogen  determination  in  the  case  of  2-ethylmercapto-5- 
methyl-6-chlorpyrimidine,  boiling  at  157°  to  159°,  gave  : 

Calculated  for 
C7H9N2SC1.  Found. 

N  14.85  15.00 


5-Mcthylcytosinc.  597 

2-Ethylmercapto-5-methyl-6-aminopyrimidinc, 

N=C—  NH, 

I  I 

CjH5SC     CCHS  .  .  —  In  the  preparation  of  this  amino  deriva- 

II  II 
N-CH 

tive,  and  also  in  the  case  of  mercaptocytosine,  the  alcoholic 
ammonia  used  should  be  thoroughly  saturated  (in  the  cold), 
as  otherwise  an  ethoxy  derivative  is  formed  instead  of  an 
amino  compound. 

We  found  that  13  grams  of  the  above  chloride  and  about  75 
cc.  of  alcoholic  ammonia,  when  heated  for  three  hours  at  127°, 
gave  10  grams  of  amino  derivative,  or  86.9  per  cent  of  the 
calculated,  and  also  that  10.1  grams  of  the  chloride,  when 
heated  for  two  hours  at  124°  to  130°,  gave  6.6  grams  of  the 
amino  base  after  crystallizing  from  50  per  cent  alcohol,  or  74 
per  cent  of  the  theoretical  amount. 

2-Bthylmercapto-5-methyl-6-aminopyrimidine  is  very  solu- 
ble in  alcohol  and  quite  difficultly  soluble  in  water.  It  crys- 
tallizes from  50  per  cent  alcohol  in  the  form  of  colorless, 
small,  stout,  six-sided  tables  and  prisms,  which  melt  at  96°  to 
97°.  It  has  a  tendency  to  separate  from  its  solutions  as  an 
oil,  which  finally  crystallizes.  A  nitrogen  determination 
gave  : 

Calculated  for 

C7HUN8S.  Found. 

N  24.86  25.20 

2-Ethylmercapto-6-ethoxypyrimidine, 


C2H5SC     CH        .  —  2-Kthylmercapto-6-chlorpyrimidine    was 

II      II 
N—  CH 

dissolved  in  alcohol  and  ammonia  gas  was  passed  in,  the  whole 
being  heated  on  the  steam-bath.  After  two  hours,  7.5  grams 
of  ammonium  chloride  had  separated,  the  calculated  quantity 
being  7.6  grams.  On  evaporating  the  alcoholic  solution  an 
oil  was  obtained  which  distilled  at  137°  to  138°  at  18  mm. 


598  Wheeler  and  Johnson. 

pressure.     A  nitrogen  determination  agreed  with  the  calcula- 
ted for  an  ethoxy  derivative  : 

Calculated  for 
C8H12ON2S.  Found. 

N  15.21  15.38 

That  this  ethoxy  derivative  is  not  an  intermediate  product 
in  the  preparation  of  the  amino  compound  was  shown  when 
on  heating  the  oil  with  alcoholic  ammonia  for  four  or  five 
hours  at  150°  to  175°  it  still  remained  unaltered. 

This  oil  dissolves  in  dilute  hydrochloric  acid  and  is  precipi- 
tated unaltered  by  ammonia.  On  boiling  for  several  hours 
with  strong  acid  it  is  converted  quantitatively  into  uracil, 
melting  at  338°.  A  nitrogen  determination  gave  25.4  per  cent 
nitrogen,  while  the  calculated  is  25.0. 

Cytosine  Dihydro chloride. — When  2-ethylmercapto-6-amino- 
pyrimidine  is  warmed  on  the  water- bath  for  three  or  four  hours 
with  concentrated  hydrochloric  acid,  then  cooled,  beautiful, 
stout,  brittle,  colorless,  flat  prisms  separate.  The  following 
analysis  shows  that  this  material  is  an  acid  salt : 

Calculated  for 

C4H5ON3.2HC1.  Found. 

Cl  38.58  39.09 

This  salt  is  analogous  to  the  acid  sulphate,  C4H5ON3. 
H2SO4,  described  by  Kossel  and  Steudel.1 

5-Methylcytosine  Monohydro  chloride  (Anhydrous}. — When 
2-ethylmercapto-5-methyl-6-aminopyrimidine  was  warmed 
with  hydrochloric  acid,  in  a  similar  manner  to  the  above, 
mercaptan  was  evolved  and  the  crystals  obtained  were  color- 
less tables  and  flat  prisms,  which,  when  dried  over  potassium 
hydroxide,  showed  signs  of  melting  at  about  270°,  and  melted 
with  effervescence  at  288°.  The  material  was  readily  soluble 
in  water.  A  chlorine  determination  showed  that  this  was  an 
anhydrous  i  :  i  salt. 

Calculated  for 

C6H7ON3.HC1.  Found. 

Cl  21.98  21.99 

When  6.6  grains  of  the  crude  mercapto  base  were  warmed 

1  Ztschr.  physiol.  Chem.,  38,  53  (1903). 


5-Methylcytosine.  599 

on  the  steam-bath  with  hydrochloric  acid  until  mercaptan 
ceased  being  evolved,  the  solution  evaporated  to  dryness,  and 
the  residue  dissolved  in  a  little  water,  0.7  gram  thymine  was 
obtained,  the  formation  of  this  being  due  to  the  presence  of 
an  ethoxy  derivative.  When  this  i  :  i  hydrochloride  was  dis- 
solved in  water  and  to  the  warm  solution  an  excess  of  ammo- 
nia was  added,  microscopic  colorless  needles  slowly  separated. 
These  were  not  very  soluble  in  hot  water  and  difficultly  in 
cold.  The  material  was  recrystallized  from  water.  The 
curious  result  was  then  observed  that  the  material  still  con- 
tained chlorine  and  that  we  had  to  deal  with  a  basic  salt  or, 
more  probably,  a  mixture  of  free  base  and  a  hydrous  basic 
salt.  The  analytical  results  agreed  fairly  with  the  calculated 
for  (C6H7ON8)62HC1.3H30. 

Calculated.  Found. 

Cl  9.4  9.09 

HaO  7.1  7.53 

The  water  determination  was  made  by  heating  the  material 
to  constant  weight  at  150°.  When  the  i  :  i  hydrochloride  is 
boiled  with  water  a  basic  salt  also  is  obtained. 

N=C— NH2 

5-Methylcytosine,    OC     CCH.     . — In   order  to   obtain  the 

I       II 
HN— CH 

free  base  the  above  material  was  dissolved  in  water,  the  chlo- 
rine was  removed  by  means  of  silver  sulphate,  the  excess  of 
silver  was  precipitated  with  hydrogen  sulphide  and  the  sul- 
phuric acid  by  barium  hydrate,  the  excess  of  the  latter  by 
carbon  dioxide.  The  clear,  colorless  solution  was  then  con- 
centrated to  a  small  volume,  whereupon,  on  cooling,  beauti- 
ful, flat,  colorless,  prismatic,  brittle  crystals  separated  that 
formed  a  sandy  powder.  When  heated,  the  crystals  gave  off 
water  above  100°  and  showed  signs  of  melting  at  240°,  melt- 
ing with  effervescence  at  2^0° ;  this  is  50°  lower  than  the 
melting-point  of  cytosine. 

100  parts  of  water  dissolved  4.5  parts  of  the  base  at  25°. 


6oo  Wheeler  and  Johnson. 

2.387  gram  substance  lost  0.1544  gram  on  heating  to  con- 
stant weight  at  135°  to  145'  (I.). 

Calculated  for  Found. 

(C5H7ON8)2.H20.  I.  II.      . 

H2O  6.71  6.46  6.30 

Calculated  for 

C6H7ON3.  Found. 

N  33-60  33.44 

Silver  nitrate,  added  to  an  aqueous  solution  of  this  base, 
gives  a  gelatinous  white  precipitate  soluble  in  an  excess  of 
ammonia  and  in  nitric  acid.  The  ammonia  solution  can  be 
boiled  without  reduction. 

Mercuric  chloride  gives  a  white  precipitate  in  dilute  solu- 
tions of  the  base ;  this  dissolves  on  heating  and  separates 
again,  on  cooling,  possibly  in  crystalline  form. 

Phosphotungstic  acid  gives  a  white  precipitate  insoluble  in 
dilute  hydrochloric  or  sulphuric  acids. 

5-Methylcytosine  Monohydrochloride  {Hydrous} . — An  attempt 
was  made  to  prepare  a  dihydrochloride  of  the  methyl  base  by 
dissolving  the  above  i  :  i  salt  in  water  and  then  saturating 
the  solution  with  hydrogen  chloride.  The  solution  was  then 
allowed  to  evaporate  spontaneously  in  a  desiccator  over  sul- 
phuric acid,  whereupon  small,  stout,  transparent  prisms  or 
rhombohedrons  separated.  The  analysis  agreed  with  the  cal- 
culated for  the  formula  C5H7ON3.HC1.2H2O. 

Calculated.  Found. 

H2O  18.2  18.0 

Cl  21.98  22. 0 

On  keeping  these  crystals  in  a  closed  tube  they  became 
opaque. 

5-Methylcytosine  Basic  Hydrochloride. — Bxperiments  were 
made  to  determine  whether  or  not  5-methylcytosine  gives  a 
2  :  i  and  a  3  :  i  salt  by  mixing  solutions  of  the  base  and  the 
above  hydrochloride  in  the  required  proportions.  It  was 
found  that  when  a  strong  solution  of  the  base  (0.12  gram) 
was  mixed  with  a  warm  solution  of  the  hydrochloride  (0.153 
gram)  in  a  little  water  a  precipitate  was  formed  immediately. 
This  dissolved  on  boiling,  and  on  cooling,  little  balls  of  mi- 


5-Methylcytosinc.  601 

nute  needles  or  prisms  separated.  When  dried  over  calcium 
chloride  the  salt  was  found  to  have  the  composition  repre- 
sented by  Analysis  I.  When  two  molecular  proportions  of 
the  base  to  one  of  the  hydrous  hydrochloride  were  used  the 
same  basic  salt  was  obtained.  For  example  :  0.15  gram  of 
the  hydrochloride  was  dissolved  in  2.5  cc.  of  water  and  2.2 
grams  of  the  base  were  dissolved  in  5  cc.  of  water.  On  mix- 
ing these  solutions  at  ordinary  temperature  a  gelatinous  mass 
separated,  so  bulky  that  the  test-tube  could  be  inverted  with- 
out loss  of  the  contents.  On  warming,  the  material  dissolved 
and  on  cooling  small  prisms  separated.  Analysis  II.: 

Calculated  for  Found. 

(C6HTON8)2HC1.H20.  I.  II. 

HaO  5-9  6.2  5.9 

Cl  n.6  11.3 

This  hydrous  basic  salt  is  analogous  to  the  hydrous  basic 
cytosine  sulphate  frequently  obtained  by  Levene.1  This  salt 
has  the  formula  (C,H5ON3)4H2SO4.2H2O. 

The  corresponding  anhydrous  basic  sulphate  has  been  de- 
scribed by  Kossel  and  Steudel.2 

A  neutral  sulphate  of  cytosine  has  also  been  described  by 
Levene.3 

5-Methylcytosine  Basic  Hydrobromide. — Ten  grams  of  2-ethyl- 
mercapto-5-methyl-6-aminopyrimidine  were  boiled  with  i5cc. 
of  strong  hydrobromic  acid  for  four  hours.  The  acid  was  then 
evaporated,  whereupon  beautiful,  large,  stout  prisms  sepa- 
rated. These  crystals  were  very  soluble  in  water.  Upon 
adding  strong  ammonia  to  the  warm  aqueous  solution  an  im- 
mediate precipitate  in  the  form  of  a  fine,  crystalline  powder 
was  obtained.  The  yield  was  7  grams.  This  precipitate  was 
difficultly  soluble  in  water.  When  heated  it  sintered  at  about 
295°  and  then  decomposed  with  effervescence  at  3i9°-32O°. 
This  material  was  boiled  for  some  time  with  strong  aqueous 
ammonia ;  it  nevertheless  still  contained  bromine,  and  on 
analysis  the  following  results  were  obtained  :  The  air- dried 
salt  lost  water  very  slowly  below  150°,  dried  at  i75°-i85°. 

1  Ztschr.  physiol.  Chem.,  39,  7  ;  39,  135,  481  (1903). 
«/*«*.,  38,53(1903). 
.,  37,  405(1903). 


602  Wheeler  and  Johnson . 

0.4838  gram  lost  0.0290  gram  water  or  5.9  per  cent.  The 
calculated  for  (C5H7ON3)2HBr.H2O  is  5.1  per  cent.  The 
dried  residue  then  gave  the  following  results  : 

Calculated  for 
(C6H7ON3)2HBr.  Found. 

C  36.25  36.20 

H  4-53  4-85 

N  25.37  25.68 

This  basic  salt  was  then  treated  with  silver  sulphate  as  de- 
scribed above  in  the  case  of  the  basic  hydrochloride.  The 
free  base  obtained  agreed  in  every  particular  with  the  prep- 
aration from  the  basic  hydrochloride.  A  water  determination 
is  given  above  (II.). 

When  0.7  gram  of  this  basic  salt  was  heated  at  I5o°-i6o° 
for  three  hours  with  20  per  cent  sulphuric  acid,  0.20  gram  of 
thymine,  melting  at  325°-326°,  was  obtained.  Forty  per  cent 
of  the  material  was  therefore  hydrolyzed. 

Acetyl-5-methylcytosine,  prepared  by  dissolving  the  base  in 
acetic  anhydride,  forms  needles  from  water.  The  material 
did  not  melt  or  effervesce  below  290°  although  it  showed  signs 
of  decomposition  at  about  255°. 

5-Methylcyto$ine  Picrate. — When  0.238  gram  of  the  base  in 
a  little  water  was  mixed  with  40  cc.  of  a  saturated  aqueous 
solution  of  picric  acid,  an  immediate  precipitate  was  formed. 
This  dissolved  on  boiling  and  adding  more  water;  on  cooling, 
long,  slender,  bright  yellow,  needle-like  prisms  separated. 
On  heating,  this  material  showed  signs  of  change  at  about  250°- 
255°  and  from  then  on  got  darker  until  at  286°  it  decomposed 
with  effervescence.  A  certain  mixture  of  this  material  with 
pure  cytosine  picrate  began  to  change  color,  on  heating,  at 
255°  and  melted  with  effervescence  at  273°.  It  is  noteworthy 
that  this  picrate  has  the  same  solubility  in  water  as  cytosine 
picrate.1  One  hundred  parts  of  water  dissolve  0.07  part  of 
the  salt. 

The  chloroplatinate  is  quite  soluble  in  water.  The  aqueous 
solution,  on  standing  in  a  desiccator,  deposits  small  orange- 
colored  rosettes. 

1  Wheeler  and  Johnson  :  Loc.  cit. 


5-Methylcytosine.  603 

2-Ethylmercapto-5-brom-6-oxypyrimidiney 
HN— CO 

CjH6SC     CBr. When      2-ethylmercapto-6-oxypyrimidine 

'    II      II 
N— CH 

(5.55  grams)  was  dissolved  in  three  parts  of  glacial  acetic  acid 
and  one  molecular  proportion  of  bromine  was  added  (6  grams) , 
a  mass  of  needles  separated ;  these  were  washed  with  water  and 
dried  ;  the  weight  was  7.45  grams  or  89  per  cent  of  the  calcu- 
lated. In  another  experiment  16  grams  of  the  mercapto  com- 
pound gave  22.1  grams  of  the  brom-derivative  or  91.7  per  cent 
of  the  theoretical  amount.  This  material  was  difficultly  sol- 
uble in  water,  but  more  readily  soluble  in  alcohol,  from  which 
solution  beautiful,  colorless,  needle-like  prisms  were  obtained. 
These,  on  heating,  showed  signs  of  change  at  about  184°  and 
melted  completely  without  effervescence  at  189°.  A  nitrogen 
determination  gave : 

Calculated  for 

C6H7ON2SBr.  Found. 

N  11.9  12. i 

An  excess  of  bromine  does  not  effect  further  substitution  in 
the  cold.  When  the  substance  is  boiled  with  hydrochloric 
acid,  5-bromuracil  is  obtained.1  Dr.  Merriam  found  that  when 
this  latter  substance  was  heated  with  aqueous  ammonia  to 
1 80°,  5-aminouracil  resulted,  the  compound  being  identified 
by  means  of  its  picrate.8 

The  action  of  alcoholic  ammonia  on  the  brommercapto 
compound  at  temperatures  between  140°  and  200°  did  not  lead 
to  a  smooth  result. 

2-Ethylmcrcapto-5-brom-6-chlorpyrimidine, 
N^CCl 

I  I 

C.H5SC     CBr. — 2-Ethylmercapto-5-brom-6-oxy  p  y  r  i  m  i  di  n  e 

II  II 
N— CH 

(21  grams)  and  phosphorus  pentachloride  (18.6  grams)  were 
mixed  and  warmed  on  the  steam-bath.  After  standing  over 

1  Wheeler  and  Merriam  :  Loc.  cit. 

2  Behrend  and  Grunwald  :  Ann.  Chem.  (I,iebig),  309,  258  (1899). 


604  Wheeler  and  Johnson. 

night  the  phosphorus  oxychloride  was  removed  by  distilling 
under  diminished  pressure  and  the  remaining  oil  poured  off 
from  a  small  amount  of  resin  ;  this  was  washed  with  a  little 
ether.  The  weight  of  crude  oil  then  obtained,  on  evaporating 
the  ether,  was  20.5  grams  or  92  per  cent  of  the  calculated. 
On  standing,  this  oil  solidified  in  the  form  of  soft,  talc-like, 
colorless  plates  which,  when  pressed  on  paper,  melted  at 
about  27°.  A  nitrogen  determination  then  gave  : 

Calculated  for 

C,H6N2SClBr.  Found. 

N  1 1 .04  ii  .06 

2-Elhylmercapto-5-brom-6-aminopyrimidtne> 
N=C— NH, 

C2H6SC     CBr        . — The   above  chlorobromide    (19  grams) 

II      II 
N— CH 

was  heated  with  alcoholic  ammonia  (40  cc.  cold  saturated 
solution)  to  1 60°  for  four  hours.  On  cooling,  a  crystalline 
mass  separated  with  little  or  no  color.  Water  was  added  to 
the  contents  of  the  tube  ;  the  material  that  separated,  on  dry- 
ing, weighed  15.7  grams  or  89.7  per  cent  of  the  calculated. 
The  substance  was  readily  soluble  in  hot  alcohol  and  diffi- 
cultly in  cold,  and  very  difficultly  soluble  in  hot  water.  On 
crystallizing  from  alcohol  it  formed  beautiful,  colorless  prisms 
which  melted  sharply  at  123°  to  124°.  The  material  con- 
tained sulphur  and  bromine,  and  a  nitrogen  determination 
gave  the  following  result : 

Calculated  for 
C«H8N«SBr.  Found. 

N  17.9  17.8 

N=C— NH2 

5-Bromcytosine,    OC     CBr        .  —  Twelve    grams    of     the 

I       II 
HN— CH 

above  mercapto  compound  were  boiled  with  50  cc.  of  con- 
centrated hydrochloric  acid  for  four  or  five  hours.  The  acid 
was  then  evaporated  and  the  residue  crystallized  from  water, 


5-Meihylcytosinc.  605 

whereupon  minute  prisms  of  the  hydrochloric  acid  salt  were 
obtained.  To  the  hot  solution  of  this  material  strong  ammo- 
nia was  added  in  excess,  and  then,  on  cooling,  bunches  of 
needle-like  prisms  of  the  free  base  separated.  The  yield  was 
7.5  grams,  or  77.3  per  cent  of  the  calculated,  more  being  ob- 
tained from  the  mother-liquor.  When  the  pure  base,  crys- 
tallized from  water,  was  heated  it  gave  no  definite  melting- 
point  but  decomposed  rapidly  above  235°.  A  nitrogen  deter- 
mination gave  : 

Calculated  for 
C4H4ON8Br.  Found. 

N  22.10  22.11 

When  this  material  was  heated  at  155°  to  190°  with  con- 
centrated aqueous  ammonia  for  four  hours,  the  products  were 
a  black  resin  and  a  brick-red  amorphous  powder,  the  material 
having  undergone  decomposition. 

N— C— NH— NO2 

Nitrocytosine,    OC     CH  . — Two  grams  of  anhy- 

I       II 
HN— CH 

drous  cytosine  (synthetic),  4.  cc.  of  concentrated  nitric  acid, 
and  4  cc.  of  concentrated  sulphuric  acid  were  mixed  and 
warmed  for  a  few  minutes  at  85°.  The  mixture  was  then 
poured  upon  crushed  ice  and  neutralized  (slight  excess  of 
ammonia  added).  The  crystalline  material  that  separated 
weighed  1.8  grams,  or  64  per  cent  of  the  calculated.  In  an- 
other experiment  2  grams  of  cytosine  and  6  cc.  of  each  acid 
gave  1.7  grams  of  the  crude  nitro  compound.  This  nitro 
compound  is  very  difficultly  soluble  in  water,  from  which  it 
separates,  in  the  form  of  colorless,  minute  needles.  These  are 
readily  soluble  in  strong  ammonia.  When  heated,  the  ma- 
terial begins  to  turn  brown  at  about  280°,  decomposes  rapidly 
above  300°,  but  does  not  melt  or  effervesce  at  350°.  A  nitro- 
gen determination  gave  the  following  result : 

Calculated  for 

C4H4O3N4.  Found. 

N  35.89  35.80 

When  an  attempt  was  made  to  reduce  this  material  with 


606  5-Methylcytosine. 

tin  and  hydrochloric  acid  the  only  crystalline  material  ob- 
tained was  ammonium  chloride.  According  to  Behrend  and 
Griinwald1  5-nitrouracil  gives  80  per  cent  of  the  calculated  of 
aminouracil,  when  reduced  in  ammoniacal  solution  by  means 
of  aluminium  amalgam.  An  attempt  to  reduce  our  nitrocyto- 
sine  in  a  similar  manner  gave  nothing  but  amorphous  yellow 
and  blue-black  decomposition-products.  For  this  reason  the 
above  nitramide  structure  is  assigned  to  the  compound. 

NEW  HAVBN,  CONN.,  Feb.  i,  1904. 
i  Loc.  cit. 


[Reprinted  from  the  American  Chemical  Journal,  Vol.  XXXII,  No.  2. 
August,  1904.] 


Contributions  from  the  Sheffield  Laboratory  of  Yale  University. 

CXV.— RESEARCHES  ON  PYRIMIDINES.     SYNTHE- 
SIS OF  2-AMINO-5-METHYIv-6-OXYPYRIMI- 

DINE. 
[SIXTH  PAPER.] 

BY  TRKAT  B.  JOHNSON  AND  SAMUEL  H.  CLAPP. 

In  a  previous  paper  from   this  laboratory,   Wheeler   and 


Syn thesis  of  2- A  mino-^ -methyl-  6-oxypyrimidine.        131 

Johnson1  described  the  two  monoaminooxypyrimidines  which 
can  give  uracil  on  hydrolysis,  viz.,  2-aminooxypyrimidine 
(Formula  I.),  and  2-oxy-6-aminopyrimidine or  cytosine  (For- 
mula II.): 

NH— CO  Nz=zC.NH2 

II  II 

H2NC         CH  OC         CH 

II          II  I          II 

N CH  NH— CH 

I.  II. 

In  a  similar  manner  the  two  monoaminomethylpyrimidines 
which  could  give  thymine  on  hydrolysis  are,  viz.,  2-oxy-6- 
amino-5-methylpyrimidine  (Formula  III.)  and  2-amino-6- 
oxy-5-methylpyrimidine  (Formula  IV.)  : 

NH— CO 

H2NC          C.CH, 

II          II 

NH-CH  N CH 

III.  IV. 

Wheeler  and  Johnson2  in  a  recent  paper  have  described 
2-oxy-6-amino-5-methylpyrimidine  (Formula  III.)  and  have 
shown  that  it  is  more  or  less  readily  converted  into  thymiue 
on  hydrolysis. 

We  will  describe  in  this  paper  the  second  monoamino- 
methylpyrimidine  (Formula  IV.),  which  theoretically  could 
give  thymine  on  hydrolysis,  viz.,  2-amino-5-methyl-6-oxy- 
pyrimidine.  We  have  synthesized  this  aminopyrimidine  by 
condensing  guanidine  with  the  sodium  salt  of  formylethyl- 
propionate.  We  have  not  only  been  able  to  obtain  the 
pyrimidine  base  which  we  desired,  but  have  also  succeeded 
in  isolating  intermediate  products  in  the  reaction.  These 
have  given  us  a  more  thorough  insight  into  the  mechanism  of 
these  pyrimidine  condensations. 

We  find,  namely,  that  in  this  condensation  there  are  three 
steps  in  the  reaction — first  a  condensation  of  guanidine  with 

1  This  JOURNAL,  29,492  (1903). 

2  Ibid.,  3 1,  592  (1904). 


132  Johnson  and  Clapp. 

the  formyl  group  of  the  sodium  formylethylpropionate  giving 
an  acrylic  ester  (Formula  V.),  then  a  saponification  of  the 
acrylic  ester  to  the  free  acid  (Formula  VI.),  and  finally  a 
condensation  to  the  pyrimidine  with  loss  of  a  molecule  of 
water  : 

NH2  COOC2H5 

H2N.C       +          C.CH3          = 

II  II 

NH         NaOCH 

NH2   COOC2H5  NH,     COOH  NH— CO 

II  II  II 

H,NC        CH3  —  H2NC         CH3       ~  H2NC         CHS 


N CH  N CH  N CH 

V. 

Under  the  conditions  by  which  we  worked  we  did  not  ob- 
serve the  formation  of  the  intermediate  guanidineacrylic  es- 
ter, but  have  evidence  of  its  existence  because  of  the  fact  that 
we  have  been  able  to  isolate  the  intermediate  guanidine- 
methylacrylic  acid.  Miiller1  has  described  two  substituted 
acrylic  acids  that  are  analogous  to  our  intermediate  acid. 
He  found  that  phenylurea  and  methylurea  readily  condensed 
with  oxalethylacetate,  giving  a  phenyluracilcarboxylic  ester 
and  methyluracilcarboxylic  ester.  By  dissolving  these  two 
esters  in  alkali  and  treating  with  strong  hydrochloric  acid 
they  were  decomposed  into  uramidoacrylic  acids  (Formulas 
VII.  and  VIII.)  : 

NH2    COOH  NH2    COOH 

II  II 

OC          CH  OC         CH 

I           II                                         I  II 

C6H5N CH  CH3N CH 

VII.  VIII. 

Behrend,2  in  his  synthesis  of  methyluracil  from  acetoacetic 
ester  and  urea,  was  able  to  isolate  an  intermediate  uramido- 
crotonic  ester,  but  was  unable  to  isolate  the  free  acid  from  its 

1  J.  prakt.  Chem.,  56,  475. 

a  Ann.  Chem.  (lyiebig),  329,  8. 


Synthesis  of  2-Amino-5-methyl-6-oxypyrimidinc.        133 

sodium  or  potassium  salt  on  account  of  the  ease  with  which  it 
condensed  to  the  pyrimidine. 

We,  furthermore,  have  made  the  interesting  observation 
that  our  intermediate  a-methyl-y#-guanidineacrylic  acid  is 
capable  of  existing  in  two  isomeric  modifications.  One  acid 
melts  at  331°  to  332°  C.  with  violent  effervescence  ;  the  other 
at  318°  to  320°  C.  to  a  clear  oil.  Both  acids  can  be  converted 
by  treatment  with  alkali  into  the  2-amido-5-methyl-6-oxy- 
pyrimidine. 

It  appears  to  us  that  the  explanation  for  this  interesting 
case  of  isomerism  is  that  we  are  dealing  with  an  ethylene 
linking,  and  have  another  case  of  cis  and  trans  isomerism  : 

CH3— C— COOH  CH8— C— COOH 

II  II 

H— C— N=C(NH1)J  (H2N)SC=N— C— H 
IX.  X. 

Cis.  Trans. 

Wislicenus1  was  able  to  isolate  three  isomeric  modifications 
of  formylphenylethylacetate.  He  represented  their  structure 
.as  follows  : 

C6H5.CH.COOC2H5     C6H5.C.COOC2H5    C6H5— C— COOC2H5 

CHO  H-C— OH  HO— C— H 

XI.  XII.  XIII. 

He  furthermore  showed  that  the  enol  form  was  capable  of 
forming  isomeric  salts,  which  gave  isomeric  acyl  modifica- 
tions when  treated  with  acyl  chlorides. 

In  a  later  paper  Wislicenus  and  Bindemann2  showed  that 
analogous  acyl  modifications  could  be  obtained  from  the 
sodium  salt  of  formylethylacetate.  Finally,  Wislicenus3 
extended  his  investigations  to  the  sodium  salt  of  formylethyl- 
propionate,  which  we  used  in  our  condensation,  and  observed 
that  this  also  gave  stereochemical  isomers  when  treated  with 
-acyl  chlorides.  The  close  analogy  between  Wislicenus'  iso- 

1  Ann.  Chem.  (I^iebig),  313,  33. 
s  Ibid.,  316,  18. 
3  Ibid.,  316,  333- 


134  Johnson  and  Clapp. 

mers  and  our  modifications  is  shown  by  the  following  formu- 
las : 

CH,— C— COOC2H8  CH3— C— COOC2H5 

II  II 

H— C— O— (OCR)  (RCO)-O— C— H 

i  i 

CH3— C— COOH  CHS— C— COOH 

II  II 

H— C— N=C(NH8)Z          (H2N)2C=N— C— H 

It  seems  probable  to  the  writer  that  Pechmann's1  isomeric 
derivatives  which  he  obtained  by  treating  the  sodium  salt  of 
formylethylacetate  with  aniline  and  paratoluidine  are  to  be 
explained  in  a  similar  manner  : 

H— C— COOC2H5  H— C— COOC2H5 

II  it 

H— C— NHR  RHN— C— H 

XIV.  XV. 

Erlenmeyer2  has  shown  that  ethyl  formate  can  be  condensed 
with  hippuric  ethyl  ester  by  means  of  sodium  ethylate  to  the 
sodium  salt  of  oxymethylenehippuric  ester.  We  have  pre- 
pared this  salt  and  find  that  it  condenses  very  smoothly  with 
pseudoethylthiourea,  giving  2-ethylmercapto-5-benzoylamino- 
6-oxypyrimidine. 

We,  furthermore,  have  condensed  ethyl  formate  with  phthal- 
imidoethylacetateto  the  sodium  salt  of  formylphthalimidoethyl- 
acetate.  We  find  that  this  salt  condenses  with  pseudoethyl- 
thiourea with  the  formation  of  2-ethylmercapto-5-phthalimido- 
6-oxypyrimidme,  and  an  intermediate  acrylic  acid. 

The  two  above  pyrimidines  show  a  most  striking  behavior 
towards  alkali.  2-Kthylmercapto-5-benzoylamino-6-oxypyrim- 
idine  dissolves  in  alkali  and  is  precipitated  unaltered  by  acids, 
while,  on  the  other  hand,  the  analogous  2-ethylmercapto-5- 
phthalimido-6-oxypyrimidine  is  converted  under  the  same  con- 
ditions into  the  corresponding  pseudoureaphthalimidoacrylic 
acid.3 

1  Ber.  d.  chem.  Ges.,  35,  1052. 

» Ibid.,  36,  3769- 

8  Since  the  above  was  written  we  have  found  that  2-ethylmercapto-5-benzoyl- 
atnino-6-oxypyrimidine  is  converted  by  alkali  into  the  sodium  salt  of  the  correspond- 
ing pseudoureabenzoylaminoacrylic  acid.  We  have  not  succeeded  in  isolating  the 
free  acid. 


Synthesis  of  2-Amino-5-methyl-6~oxypyrimidinc.        135 

NH— CO 
|          I      /COv  NaOH 

C2H$S.C        CN<         >C6H< 

II         ||    ^CO/ 

N CH 

NH2     COOH 

I  I      /COv 
C,H5SC         CN<        >C6H4. 

II  II     ^CO/ 
N CH 

EXPERIMENTAL  PART. 

NH— CO 

I  I 

2-Amino-5-mcthyl-6~oxypyrimidinc,  H2N — C         C — CHS.  — 

II  II 
N CH 

Seventy-two  grams  of  guanidine  carbonate  were  dissolved  in 
the  least  possible  quantity  of  cold  water  and  mixed  with  54 
grams  of  barium  hydroxide  dissolved  in  400  cc.  of  water.  To 
this  solution,  filtered  clear  from  the  precipitated  barium  car- 
bonate, 283  grams  of  crude  sodium  formylethylpropionate 
were  added.  After  standing  at  ordinary  temperature  for 
about  eight  hours  the  clear  solution  was  divided  into  two 
equal  parts.  One  part  was  heated  on  the  steam-bath  for 
about  half  an  hour  and  then  neutralized  with  dilute  sulphuric 
acid.  A  brown  precipitate  separated  immediately  and  was 
filtered  off  and  saved  (see  tran s  acid).  The  clear  solution 
that  remained  was  evaporated  to  dryness,  then  redissolved  in  a 
little  warm  water,  and  filtered  from  a  small  amount  of  insolu- 
ble material  that  was  present.  The  pyrimidine  base  was  then 
precipitated  with  phosphotungstic  acid,  the  tungstic  acid  pre- 
cipitate decomposed  with  barium  hydroxide,  and  the  excess 
of  barium  hydroxide  removed  in  the  usual  way  with  carbon 
dioxide.  On  concentrating  the  solution  that  remained,  and 
cooling,  the  base  separated  in  the  form  of  stout  prisms  and 
melted  with  effervescence  at  320°  to  321°. 

The  second  part  of  the  original  solution  was  allowed  to 
stand  at  ordinary  temperature  for  two  weeks.  It  was  then 
neutralized  with  dilute  sulphuric  acid  as  before.  An  insolu- 


136  Johnson  and  Clapp. 

ble  brown  precipitate  was  obtained  as  in  the  first  part. 
After  filtering  off  this  insoluble  precipitate  we  precipitated  the 
pyrimidine  base  with  mercuric  chloride  instead  of  phospho- 
tungstic  acid.  The  mercury  was  removed  from  the  precipi- 
tate with  hydrogen  sulphide  and  then  the  base  allowed  to 
crystallize  from  the  concentrated  solution. 

The  yield  of  pure  base  by  the  two  different  methods  of 
treatment  was  about  equal  (4  grams),  showing  that  long 
standing  does  not  increase  to  any  extent  the  yield.  The 
same  observation  was  made  by  Wheeler  and  Johnson1  in  their 
preparation  of  isocytosine  or  2-amino-6-oxypyrimidine. 

2-Amido-5-methyl-6-oxypyrimidine  crystallized  from  hot 
water  in  two  distinct  crystalline  forms,  stout  prisms,  and  long, 
slender,  needle-like  prisms.  It  melts  at  320°  to  321°  with  vio- 
lent effervescence.  It  does  not  contain  water  of  crystalliza- 
tion. One  hundred  parts  of  water  dissolve  0.43  part  base  at 
25°  C.  A  nitrogen  determination  gave  : 

Calculated  for  Found. 

C5H7ON3.  I.  II. 

N  33.60  33.68  33.91 

The  base  was  not  hydrolyzed  to  thymine  after  heating  in  a 
sealed  tube  with  25  per  cent  sulphuric  acid  for  five  hours. 

In  a  second  condensation  we  modified  our  experiment  in 
the  following  manner :  After  adding  the  sodium  formyl- 
ethylpropionate  to  the  guanidine  solution,  we  added  a  molec- 
ular proportion  of  sodium  hydroxide  (29  grams).  The  alka- 
line solution  was  then  allowed  to  stand  at  a  temperature  of 
40°  to  50°  for  about  ten  hours,  and  then  heated  on  the  steam - 
bath  for  three  hours.  The  solution  was  then  divided  into  two 
equal  parts  and  one  part  neutralized  with  acetic  acid,  the 
other  with  dilute  sulphuric  acid.  An  immediate  precipitate 
of  the  trans  acid  resulted  in  both  cases.  The  weight  of  in- 
soluble acid  obtained  here  was  12.2  grams. 

The  two  filtrates  were  combined  and  precipitated  with  an 
excess  of  mercuric  chloride.  The  mercury  was  removed  in 
the  usual  way  with  hydrogen  sulphide  and  the  filtrate  con- 
centrated. On  cooling  the  concentrated  solution  we  obtained 

1  Loc,  cit. 


Synthesis  of  2-Amino-5-methyl-6-oxypyrimidine.        137 

a  mass  of  needle-shaped  prisms  mixed  with  stout  prisms. 
Some  of  these  needle- formed  prisms  melted  at  319°  to  320°  to 
a  clear  oil,  followed  by  a  slow  effervescence.  That  this  body 
was  not  the  same  product  as  we  obtained  in  our  first  conden- 
sation was  shown  by  the  fact  that  when  it  was  mixed  with 
the  free  pyrimidine  the  melting-point  was  lowered  to  308°- 
310°  (see  cis  acid).  The  yield  of  this  crystalline  product  was 
18.2  grams. 

Behavior  with  Alkali. — The  base  dissolves  very  readily  in 
the  cold  in  both  dilute  (2  per  cent)  and  strong  (9  per  cent) 
solutions  of  sodium  hydroxide,  and  is  precipitated  unaltered 
when  the  alkaline  solution  is  neutralized  with  carbon  dioxide 
or  dilute  sulphuric  acid.  It  separates  in  the  form  of  needle- 
formed  prisms  and  melts  at  320°  to  321°  with  violent  efferves- 
cence. In  appearance  this  crystalline  form  of  the  base  re- 
sembles very  much  that  of  the  cis  acid.  That  the  ring  is  not 
opened  by  the  treatment  with  alkali  is  shown  by  the  fact  that 
when  this  body  was  mixed  with  the  cis  acid  the  melting-point 
was  lowered  to  307°.  Furthermore,  a  nitrogen  determination 
gave: 

Calculated  for 

C5H7ON3.  Found. 

N  33.60  33.90 

The  Hydro  chloride. — Some  of  the  base  was  dissolved  in  con- 
centrated hydrochloric  acid  and  the  solution  concentrated  in  a 
vacuum.  The  hydrochloride  separated  in  stout  prisms.  A 
chlorine  determination  agreed  with  the  calculated  for  mono- 
hydrochloride  : 

Calculated  for 

C6H7ON3.HC1.  Found. 

Cl  21.98  21.73 

The  Picrate. — The  picrate  separated  immediately  from 
water  in  yellow,  microscopic  crystals.  They  were  practically 
insoluble  in  boiling  alcohol  and  water.  After  prolonged  boil- 
ing with  water  the  insoluble  picrate  was  filtered  off  and  ana- 
lyzed for  nitrogen  : 

Calculated  for 
C5H7ON3.C6H3O7N3.  Found. 

N  23.73  23.92 


138  Johnson  and  Clapp. 

The  Sulphate. — The  sulphate  crystallized  from  water  in  the 
form  of  flattened  prisms  or  plates.  A  sulphur  determination 
agreed  with  the  calculated  for  an  acid  salt.  It  is  interesting 
to  note  that  Jaeger1  obtained  analogous  acid  sulphates  from 
the  isomeric  2-amido-4-methyl-6-oxypyrimidine,  and  from 
2-atnido-4,5-dimethyl-6-oxypyrimidine  : 

Calculated  for 
CsH^ONs.HaSO^  Found. 

S  14.34  14-62 

Platinum  Chloride  Double  Salts. — Two  characteristic  plati- 
num chloride  double  salts  were  obtained.  The  first  was  pre- 
pared by  adding  hydrogen  platinic  chloride  to  a  cold,  dilute 
hydrochloric  acid  solution  of  the  base.  It  analyzed  for  a  salt 
with  4  molecules  of  water  of  crystallization  : 

Calculated  for  Found. 

(C6H7ON3.HCl)2PtCl4.4HsO.  I.  II. 

Pt  26.56  26.51  26.6l 

When  hydrogen  platinic  chloride  was  added  to  a  hot  hydro- 
chloric acid  solution  of  the  base  and  then  the  solution  allowed 
to  cool  slowly,  the  platinum  salt  separated  in  thick  tables  and 
melted  at  254°  to  255°.  A  water  determination  and  an  analy- 
sis for  platinum  agreed  with  the  calculated  for  a  double  plat- 
inum salt  containing  two  molecules  of  water  of  crystallization  : 

0.1995  gram  salt  lost  0.0106  gram  H2O  at  120°  to  130°  C. 

Calculated  for 
(C6H7ON3.HC1)2PtCl4.2H2O.  Found. 

Pt  27.99  27.76 

H,O  5.17  5.30 

Trans- a- Methyl-  fi-guanidineacrylic  A cid, 

CH8— C— COOH 

||  . — This  acid  was  always  obtained 

(H2N),C=N— C— H 

in  the  condensation  described  above,  when  we  neutralized  the 
alkaline  solution,  preliminary  to  precipitating  the  pyrimidine 
base  with  mercuric  chloride.  It  separated  as  an  amorphous 
brown  precipitate.  One  of  the  most  characteristic  physical 
properties  that  distinguished  this  acid  from  its  cis  modification 
and  the  pyrimidine  was  its  insolubility  in  water.  One  hun- 

1  Ann.  Chem.  (Liebig),  a6a,  371. 


Synthesis  of  2-Amino-5-methyl-£>-oxypyrimidine.        139 

dred  parts  of  water  dissolve  0.08  part  acid  at  25°  C.  It  crys- 
tallized from  boiling  water  in  poorly  developed  prisms,  and 
melted  according  to  the  rate  of  heating  from  329°  to  332°  with 
violent  effervescence.  It  possesses  both  acid  and  basic  prop- 
erties. A  nitrogen  determination  gave  : 

Calculated  for 

C5H902N3.  Found. 

N  29.37  29.32 

In  our  second  condensation  the  trans  acid  came  down  less 
pure  and  was  mixed  with  a  considerable  amount  of  stout 
prisms.  These  were  separated  by  boiling  with  water.  After 
filtering  and  cooling,  the  prisms  separated  again  and  melted 
at  320°  to  321°  with  effervescence.  That  this  was  the  pyrimi- 
dine  base  was  shown  by  the  fact  that  when  mixed  with  the 
pure  pyrimidine  the  melting-point  was  not  lowered.  The 
trans  acid  was  not  changed  to  the  cis  modification  or  the 
pyrimidine  after  boiling  in  water  for  six  hours.  A  nitrogen 
determination  in  the  above  pyrimidine,  melting  at  320°  to 
321°,  gave  : 

Calculated  for 

C6H7ON3.  Found. 

N  33.60  33.68 

Behavior  with  9  Per  Cent  Sodium  Hydroxide. — When  the 
trans  acid  was  dissolved  either  in  the  cold  or  warm  sodium 
hydroxide  solution,  and  the  solution  neutralized  with  carbon 
dioxide  it  separated  in  the  form  of  stout  prisms  and  melted  at 
320°  to  321°  with  violent  effervescence.  That  this  was  the 
pyrimidine  base  was  confirmed  by  a  nitrogen  determination  : 

Calculated  for 
C5H7ON8.  C5H9O2N8.  Found. 

N  33.60  29.37  33-52 

The  formation  of  the  pyrimidine  from  the  trans  acid  was 
furthermore  confirmed  by  the  formation  and  analysis  of  its 
platinum  chloride  salt.  It  separated  in  the  form  of  stout 
prisms  and  melted  at  254°  to  255°.  When  mixed  with  the 
double  salt  previously  described  as  melting  at  254°  to  255°  the 
melting-point  was  not  lowered.  A  platinum  determination 
gave  : 


140  Johnson  and  Clapp. 

Calculated  for 
(C5H7ON3.HCl)aPtCl4.2H2O.  Found. 

Pt  27.99  27.93 

Behavior  with  2  Per  Cent  Sodium  Hydroxide. — Some  of  the 
trans  acid  melting  at  331°  was  dissolved  in  the  cold,  dilute 
sodium  hydroxide  solution.  On  neutralizing  with  dilute  sul- 
phuric acid  it  separated  again  as  a  brown,  poorly  crystallized 
precipitate.  It  was  extremely  insoluble  in  water  and  melted 
at  330°  to  332°  with  violent  effervescence.  The  trans  acid 
was  precipitated  again  unaltered  after  this  treatment  with  di- 
lute alkali.  When  mixed  with  the  pure  analyzed  acid  the 
melting-point  was  not  lowered.  This  experiment  is  of  inter- 
est because  it  enabled  us  to  determine  the  cis  and  trans  forms 
of  our  acid.  The  isomeric  modification  could  not  be  precipi- 
tated unaltered  from  an  alkaline  solution. 

Cis- a- Methyl- ft-guanidineacrylic  Acid, 
CH8— C— COOH 

||  . — This  acid  was  obtained  in  our  sec- 

H— C— N=C(NHa)2 

ond  condensation  when  we  precipitated  with  mercuric  chlo- 
ride to  obtain  the  pyrimidine  base.  After  removing  the  mer- 
cury from  the  precipitate  with  hydrogen  sulphide  and  concen- 
trating the  solution  it  separated  with  the  pyrimidine  base  in 
slender,  needle-like  prisms.  It  was  obtained  pure  by  recrys- 
tallizing  from  hot  water.  It  was  approximately  about  twice 
as  soluble  in  water  as  the  pyrimidine.  One  hundred  parts  of 
water  dissolve  0.84  part  acid  at  25°.  The  most  noticeable 
physical  property  which  this  acid  possesses  is  its  behavior  on 
melting.  It  melts  at  319°  to  320°  to  a  clear  oil,  followed  by  a 
slight  effervescence  and  slow  decomposition.  A  nitrogen  de- 
termination gave  : 

Calculated  for  Found. 

C6H902N3.  I.  II. 

N  29.37  29.05  29.6 

In  order  to  be  certain  that  we  were  dealing  here  with  a  sec- 
ond modification  of  the  guanidineacrylic  acid,  and  not  with  a 
modification  of  our  pyrimidine  containing  water  of  crystalliza- 
tion, some  of  the  acid  was  heated  for  one  hour  at  115°  to  120°, 
and  again  at  140°  for  one  hour.  The  body  lost  no  weight  by 


Synthesis  of  2-Amino-^-methyl-6-oxypyrimidine.        141 

this  treatment,  thus  confirming  our  assumption  that  we  had 
in  hand  an  isomeric  acid. 

Behavior  with  9  Per  Cent  Sodium  hydroxide. — The  cis  acid 
dissolved  immediately  in  the  sodium  hydroxide  solution. 
When  the  alkaline  solution  was  neutralized  with  carbon  di- 
oxide or  with  dilute  hydrochloric  acid  an  asbestos-like  pre- 
cipitate of  needle-like  prisms  were  obtained.  They  melted  at 
319°  to  321°  with  effervescence.  When  mixed  with  the  pyrimi- 
dine  (m.  p.  320°)  the  melting-point  was  not  lowered.  When 
mixed  with  the  cis  acid  (m.  p.  319°  to  320°)  the  melting-point 
was  lowered  to  from  302°  to  303°.  That  the  cis  acid  had  been 
converted  into  the  pyriinidine  was  confirmed  by  a  nitrogen  de- 
termination : 

Calculated  for 

C5H7ON8.  Found. 

N  33.60  33.23 

Behavior  with  2  Per  Cent  Sodium  Hydroxide. — The  cis  acid 
that  was  used  in  this  experiment  melted  sharply  at  320°  to  a 
clear  oil  and  analyzed  for  29.05  per  cent  of  nitrogen,  calcula- 
ted 29.37  Per  cent.  It  dissolved  immediately  in  the  cold,  di- 
lute sodium  hydroxide  solution.  When  the  alkaline  solution 
was  neutralized  with  carbon  dioxide  or  sulphuric  acid  the  base 
was  precipitated  in  needle-like  prisms  melting  at  320°  with 
effervescence.  A  nitrogen  determination  agreed  with  the 
calculated  for  the  pyrimidine  : 

Calculated  for 

C5H7ON3.  Found. 

N  33.60  33.43 

Acetic  acid  also  precipitated  from  an  alkaline  solution  of 
the  cis  acid,  the  pyrimidine  melting  at  320°. 

Condensation  of  Ethyl  Formate  with  Phthalimidoethylacetate . — 
This  condensation  was  effected  by  suspending  the  phthalimido- 
ethyl acetate  in  benzene  or  ether  with  the  calculated  amount 
of  sodium  and  adding  slowly  the  ethyl  formate.  The  con- 
densation was  not  smooth,  and  after  standing  for  several 
hours,  with  occasional  shaking,  much  phthalimidoethylacetate 
remained  unaltered.  From  50  grams  of  phthalimidoethylace- 
tate about  50  grams  of  crude  sodium  salt  were  obtained. 


142  Johnson  and  Clapp. 

This  sodium  salt  is  exceedingly  unstable  in  aqueous  solu- 
tion. Some  of  the  salt  was  dissolved  in  water  and  then  fil- 
tered. When  this  clear  salt  solution  was  allowed  to  stand  for 
several  hours  at  ordinary  temperature  it  gradually  deposited  a 
crystalline  solid.  This  crystallized  from  alcohol  in  needle- 
like  prisms  and  melted  at  111°.  It  proved  to  be  unaltered 
phthalimidoethylacetate.  When  the  filtered  solution  was  acidi- 
fied with  hydrochloric  acid  no  further  precipitation  took 
place. 

On  the  other  hand,  when  a  solution  of  the  sodium  salt  was 
immediately  acidified  with  hydrochloric  acid  a  semisolid  pre- 
cipitate was  obtained.  It  was  insoluble  in  hot  water.  It 
dissolved  in  cold  alcohol  with  the  exception  of  a  small  amount 
of  white,  crystalline  material.  This  insoluble  product  crys- 
tallized from  hot  alcohol  in  needles  and  melted  at  193°  to  194°. 
It  was  soluble  in  alkali  to  a  yellow  solution.  This  body  was 
identified  as  4-oxyisoquinoline-3-carboxylic  ethyl  ester,  which 
was  obtained  by  Gabriel  and  Colman1  by  heating  phthalimido- 
ethylacetate with  sodium  ethylate  and  alcohol  at  100°.  A 
nitrogen  determination  gave  : 

Calculated  for 
Ci2HnO4N.  Found. 

N  6.0O  6.21 

When  the  above  alcoholic  extract  was  evaporated  to  dry- 
ness  a  thick  syrup  was  obtained  which  immediately  solidified 
on  cooling.  It  crystallized  from  alcohol  in  prisms  and  melted 
at  ni°  to  112°.  It  was  identified  as  phthalimidoethylacetate. 

2-  Ethylmercapto-^-phthalimido-6-oxypyrimidine , 
NH— CO 

I       I     /cov 

C2H5S.C         C.N<         J>C6H4.— Tbispyrimidine  wasobtained 

II          II      XCO' 

N=CH 

by  condensing  pseudoethylthiourea  in  aqueous  solution  with 
the  sodium  salt  of  formylphthalimidoethy  lacetate.  Six  and  two- 
tenths  grams  of  the  crude  salt  were  treated  with  160  cc.  of 
water  and  filtered  from  the  unaltered  phthalimidoethylacetate. 
To  the  clear  solution  was  then  added  an  aqueous  solution  of 

1  Ber.  d.  chem.  Ges.,  33,  983. 


Synthesis  of  2-Amino-^-methyl-6-oxypyrimidine.        143 

the  pseudourea,  that  was  prepared  by  mixing  a  solution  of  36 
grams  of  the  hydrobromide  with  1  1  grams  of  potassium  hydrox- 
ide. The  resulting  mixture  was  then  allowed  to  stand  at  ordi- 
nary temperature  for  one  hour,  and  then  heated  on  the  steam- 
bath.  Mercaptan  was  evolved  in  large  amount,  and  on  prolonged 
heating  the  solution  assumed  a  dark-green  color.  A  crystal- 
line precipitate  finally  began  to  separate  from  the  hot  solution 
when  the  mixture  was  removed  from  the  bath  and  allowed  to 
cool.  This  crystalline  body  proved  to  be  phthalimidoethyl- 
acetate.  On  acidifying  the  solution  with  sulphuric  acid  a 
thick,  gummy  precipitate  was  obtained,  which  was  purified 
by  boiling  with  water  and  animal  charcoal.  It  crystallized 
from  alcohol  in  rhombic  plates  and  melted  at  230°  to  231°  to  a 
yellow  oil.  It  gave  a  strong  test  for  sulphur.  A  nitrogen 
determination  gave  : 

Calculated  for 

Found. 


N  13-95  14-3 

When  the  above  pyrimidine  was  dissolved  in  alkali  and 
then  acidified  with  dilute  hydrochloric  or  sulphuric  acid  a 
white,  crystalline  precipitate  was  immediately  obtained.  It 
crystallized  from  50  per  cent  alcohol  and  melted  with  violent 
effervescence  at  130°  to  131°,  then  solidified  again  in  the  hot 
bath,  and  did  not  melt  again  until  229°  to  a  clear,  yellow  oil. 
It  gave  a  strong  test  for  sulphur.  A  nitrogen  determination 
agreed  with  the  calculated  for  «-phthalimido-/?-pseudoethyl- 
thioureaacrylic  acid, 

C6H4(CO),N—  C(COOH)=CH.N=C(SC2H5)—  NH,  : 

Calculated  for 
CHH18O4N8S.  Found. 

N  13.16  13.26 

This  same  acid  was  obtained  in  the  above  condensation 
when  the  acid  filtrates  were  allowed  to  stand.  It  separated 
in  small  prisms  and  was  purified  by  crystallizing  from  alcohol. 
When  the  acid  was  heated  above  its  melting-point  in  an  oil- 
bath  it  immediately  decomposed  with  loss  of  a  molecule  of 
water,  giving  the  pyrimidine  derivative  melting  at  231°. 


144  Johnson  and  Clapp. 

When  mixed  with  the  pyrimidine  the  melting-point  was  not 
lowered. 

Sodium  Salt  of  Oxymethylenehippuric  Ethyl  Ester, 

yNH.COC6H6 
NaO— CH— C^  .—This  salt  was  used  by  Erlen- 

NCOOC2H5 

meyer1  in  his  synthesis  of  serine  and  cystine.  He  gives  no 
directions  for  preparing  the  salt,  but  states  that  he  obtained 
it  by  condensing  ethyl  formate  with  hippuric  ethyl  ester  in 
presence  of  sodium  ethylate. 

We  have  prepared  the  salt  by  condensing  hippuric  ethyl 
ester  with  ethyl  formate  in  benzene  in  the  presence  of  metallic 
sodium.  The  condensation  is  very  slow.  From  25  grams  of 
hippuric  ester  we  obtained  35  grams  of  the  crude  salt. 

2-Ethylmercapto-5-benzoylamino-6-oxypyrimidine, 
NH— CO 

I  I 

C2H5S.C          CNH.COC6H5.— Thirty-five  grams  of  the  above 

II  II 
N CH 

sodium  salt  were  dissolved  in  cold  water  and  combined  with 
an  aqueous  solution  of  pseudoethylthiourea.  Only  0.5  molec- 
ular proportion  of  pseudourea  was  used  in  this  reaction,  or  13 
grams  of  the  hydrobromide,  which  were  neutralized  with  4 
grams  of  potassium  hydroxide.  The  mixture  was  allowed  to 
stand  at  ordinary  temperature  for  forty-eight  hours.  No  odor 
of  mercaptan  was  noticeable.  When  the  mixture  was  ex- 
amined a  large  amount  of  crystalline  material  had  separated 
from  the  aqueous  solution.  This  crystallized  from  alcohol  in 
needles  and  melted  at  238°  to  239*  to  a  yellow  oil.  It  gave  a 
strong  test  for  sulphur  and  did  not  decompose  when  heated  to 
260°.  A  nitrogen  determination  gave  : 

Calculated  for 
Ci3H13O2N3S.  Found. 

N  15.27  15.50 

The  pyrimidine  was  soluble  in  alkali  and  was  precipitated 
unaltered  by  hydrochloric  acid. 

1  Ber.  d.  chem.  Ges.,  36,  3769;  35,  2720. 


Synthesis  of  2-Amino-^-methyl-^-oxypyrimidine.         145 

When  the  alcoholic  filtrates  from  the  above  purification 
were  combined  and  evaporated  to  dryness  an  oil  was  obtained 
which  finally  solidified.  It  was  identified  as  unaltered  hip- 
puric  ester. 

More  of  the  above  pyrimidine  was  obtained  by  acidifying 
the  original  solution  after  filtering  off  the  crystalline  material 
that  had  separated.  It  was  precipitated  as  a  semisolid, 
which  quickly  solidified  on  cooling.  It  crystallized  from  alco- 
hol in  needles  and  melted  at  238°  to  239°. 

NEW  HAVEN,  CONN.,  Feb.  24,  1904. 


[Reprinted  from  the  American  Chemical  Journal,  Vol.  XXXII,  No.  4. 
October,  1904.] 


Contributions  from  the  Sheffield  Laboratory  of  Yale  University. 

CXIX.— RESEARCHES    ON    PYRIMIDINES :    2-OXY- 

4,6-DIAMINOPYRIMIDINE.1 

[SEVENTH  PAPER.] 

BY  HENRY  I,.  WHEELER  AND  GEORGE  S.  JAMIESON. 

In  this  paper  we  describe  a  number  of  pyrimidines  derived 
from  2-thiobarbituric  acid.     Our  chief  object  in  investigating 

1  Part  of  a  thesis  presented  by  Mr.  G.  S.  Jamieson  for  the  degree  of  Doctor  of 
Philosophy,  Yale  University,  1904. 


2-  Oxy-j. ,  6-dia  minopyri midine.  343 

these  compounds  was  to  prepare   2-0x7-4, 6-diaminopyrimi- 
dine. 

Kutscher1  believes  lie  obtained  an  oxydiaminopyrimidine 
from  yeast  nucleic  acid,  the  acid  having  been  decomposed  by 
sulphuric  acid  at  a  high  temperature  and  under  pressure. 
He  considers  the  substance  as  differing  from  cytosine  inas- 
much as  a  hydrogen  atom  is  replaced  by  an  amino  group. 

It  may  be  added  that  since  the  pyrimidine  derivatives 
hitherto  obtained  from  nucleic  acids  have  an  oxygen  atom  in 
the  2-position,  for  example,  uracil,  thymine,  and  cytosine,  it 
is  probable  that  a  diamino  derivative  would  be  similarly  con- 
stituted. This  being  the  case,  there  are  only  two  oxydiamino- 
pyrimidines  that  fulfil  these  conditions,  namely,  2-oxy-4,6- 
diaminopyrimidine  (I.)  and  2-oxy-5,6-diaminopyrimidine 
(II.)  : 

N C— NH2  N C— NH2 

OC  C— NH2 

I  II 

HN CH 

II. 

Our  first  attempts  to  prepare  the  oxydiaminopyrimidine 
represented  by  Formula  I.  were  as  follows  :  2-Thiobarbituric 
acid  (III.)  was  prepared  by  the  method  of  Michael.2  It  was 
found  that  this  substance  could  be  converted  into  2-methyl- 
mercapto-4,6-dioxypyrimidine  (IV.)  by  means  of  sodium, 
ethylate  and  methyl  iodide  in  alcoholic  solution  : 

HN CO  HN CO  N=   =CC1 

II  II  II 

SC  CH2    ~     CH,SC  CH2     ~     CH8SC  CH 

II  II  I  II  II 

HN CO  N CO  N CC1 

III.  IV.  V. 

When  the  mercapto  derivative  (IV.)  was  heated  on  the 
steam-bath  with  2  molecular  proportions  of  phosphorus  penta- 
chloride,  it  was  converted  into  2-methylmercapto-4,6-dichlor- 
pyrimidine  (V.).  The  reaction  was  not  smooth  and  a  con- 

1  Ztschr.  physiol.  Chem.,  38,  176  (1903). 

2  J.  prakt.  Chem.,  35,  456  (1887)  ;  49,  38  (1894). 


344  Wheeler  and  Jamieson. 

siderable  amount  of  decomposition-products  was  always  ob- 
tained. It  was  later  observed  that  the  dichloride  could  be 
obtained  more  smoothly  by  using  phosphorus  oxychloride  in- 
stead of  the  pentachloride. 

When  the  dichloride  was  heated  with  alcoholic  ammonia  it 
was  found  that  only  one  chlorine  atom  was  easily  removed 
and  2-mercapto-5-chlorcytosine  (VI.)  was  formed.  This  took 
place  at  temperatures  ranging  from  125°  to  about  190°.  Even 
below  the  latter  temperature  mercaptan  was  evolved,  and 
above  190°  2,4,6-triaminopyrimidine  (VIII.),  which  has  been 
described  by  Gabriel,1  was  obtained.  There  seemed  to  be 
little  tendency  for  the  two  chlorine  atoms  to  react  without 
also  displacing  the  mercapto  group. 

The  2-mercapto-4-chlorcytosine  was  then  converted  into 
4-chlorcytosine  (VII.)  by  boiling  with  hydrochloric  acid. 
When  this  was  heated  with  alcoholic  ammonia  a  reaction  took 
place,  but  the  chief  product  was  not  the  desired  2-oxy-4,6- 
aminopyrimidine : 

N C— NH2  N— C-NH2 


CH.SC           CH 

II            II 
N  CC1 

VI. 

»- 

OC 

HN  
VII. 

CH 

II 
-CC1 

N 

H2N—  C 

II 

=:C—  NH2 

1 
CH 

ij 

II 

N 

II 
C—  NH2 
VIII. 

It  was  finally  found  that  2-oxy-4,6-diaminopyrimidine 
could  easily  be  prepared  from  2-thio-4,6-diaminopyrimidine 
(IX.)  which  Traube2  has  recently  obtained  by  condensing 
malonic  nitrile  with  thiourea.  This  substance  united  smoothly 
with  methyl  iodide  and  the  resulting  mercapto  derivative  (X.) 
formed  on  treating  the  addition-product  with  ammonia,  on 
carefully  boiling  with  hydrochloric  acid,  gave  the  2-0x3^-4,6- 
diaminopyrimidine  (I.)  : 

1  Ber.  d.  chem.  Ges.,  34,  3364. 

8  Ann.  Chem.  (Mebig),  331,  80  (1904). 


2-Oxy~4,6-diaminopyrimidine.  345 

N=C— NH2  N C— NH2         HN 

II  II  I 

SC  CH  —  CH3SC  CH  ~    OC 

I  II  II  II  I 

HN C— NH2  N C— NH2          HN 

IX.  X.  XL 

It  was  then  found  that  if  the  warming  with  hydrochloric  acid 
was  continued  for  more  than  a  short  time  on  the  steam-bath 
the  2-oxy-4,6-diaminopyrimidine  was  completely  converted 
into  barbituric  acid  (XI.)-  It  is  therefore  obvious,  from  the 
readiness  with  which  this  compound  is  decomposed  by  hydro- 
chloric acid,  that  it  is  not  identical  with  Kutscher's  new  base. 
If  the  latter  is  an  oxydiaminopyrimidine  it  probably  is  2-oxy- 
5,6-diaminopyrimidine. 

EXPERIMENTAL,  PART. 

2-  Thiobarbituric  add  was  prepared  according  to  Michael's1 
directions,  by  the  condensation  of  sodium  ethyl  malonate  with 
thiourea  in  absolute  alcoholic  solution.  Twenty-five  grams 
of  ethyl  malonate  gave  20  grams  of  crude  sodium  thiobarbitu- 
rate.  From  this  a  yield  of  12  grams  of  acid  was  obtained. 
It  was  found  that  if  instead  of  the  calculated  quantity  of  sodium 
ethylate  two  molecular  proportions  were  used  a  larger  yield  of 
the  acid  resulted.  For  example,  in  two  experiments,  using 
25  grams  of  ethyl  malonate,  27  grams  of  sodium  thiobarbitu- 
rate  were  obtained  ;  in  three  other  cases,  using  the  same  pro- 
portions, 28  grams  of  salt  separated,  the  yield  of  thiobar- 
bituric  acid  in  each  case  being  16.5  grams. 

HN CO 

I  I 
2-Methylmercaptobarbituric    Acid,    CH3SC         CH2. The 

II  I 
N CO 

best  yield  of  this  substance  was  obtained  when  12  grams  of 
thiobarbituric  acid  were  added  to  a  cold,  absolute  alcoholic 
solution  of  1.9  grams  of  sodium,  then  15  grams  of  methyl 
iodide  were  added  and  the  solution  was  not  allowed  to  warm. 
The  reaction  was  complete  in  two  days.  The  alcohol  and 

i  J.  prakt.  Chem.,  35,  456  (1887)  ;  49,  38  (1894). 


346  Wheeler  and  Jamie  son. 

excess  of  methyl  iodide  were  then  evaporated  and  the  residue 
was  treated  with  water  and  acidified  with  acetic  acid.  The 
precipitate  was  filtered,  washed  with  water,  absolute  alcohol, 
and  ether.  A  yield  of  8.6  grams  of  sodium-free  material  was 
obtained.  In  another  experiment,  40  grams  of  acid  gave  2.5 
grams  of  the  mercapto  derivative,  the  usual  yield  being  be- 
tween 53  and  66  per  cent  of  the  calculated.  Attempts  to 
methylate  thiobarbituric  acid  by  other  methods,  such  as  by 
direct  addition  of  methyl  iodide,  or  by  the  action  in  alcoholic 
ammonia,  or  in  aqueous  solution  and  in  the  presence  of  alkali, 
either  failed  entirely  or  did  not  give  as  satisfactory  results  as 
the  above  method. 

The  2-methylmercaptobarbituric  acid  crystallized  from 
water  in  needles.  It  is  sparingly  soluble  in  hot  water  and 
less  soluble  in  alcohol.  It  did  not  melt  at  300°,  but  gradually 
turned  a  light-brown.  A  nitrogen  determination  gave  : 

Calculated  for 
CsH^OaNaS.  Found. 

N  17.72  17.87 

N=CC1 

2-Methylmercapto-4,6-dichlorpyrimidine,  CH3SC  CH.  — 

II  II 

N CC1 

Four  grams  of  the  above  2-methylmercaptobarbituric  acid 
were  heated  with  9  grams  of  phosphorus  pentachloride  on  the 
steam- bath.  When  the  evolution  of  hydrogen  chloride  ceased 
the  dark-red  solution  was  cooled  and  treated  with  crushed  ice. 
The  dichloride  was  then  shaken  out  with  ether,  the  ethereal 
solution  dried  over  calcium  chloride,  evaporated,  and  the 
residue  distilled  at  28  mm.  pressure,  whereupon  2.5  grams  of 
colorless  oil  were  obtained,  boiling  at  154°,  this  being  a 
yield  of  50.2  per  cent  of  the  calculated.  In  two  other  experi- 
ments with  phosphorus  pentachloride,  using  in  each  case  8 
grams  of  the  methylmercaptobarbituric  acid,  3  grams  and  3.7 
grams  of  dichloride  were  obtained.  Both  specimens  boiled  at 
135°  to  136°  at  14  mm.  pressure.  The  oil  thus  obtained 
solidified  in  the  form  of  table-like  prisms,  which  melted  at 
41°  to  42°.  When  phosphorus  oxychloride  was  used  instead 


347 

of  the  pentachloride,  the  remaining  treatment  being  the  same, 
the  dichloride  was  directly  obtained  in  the  crystalline  condi- 
tion, it  being  unnecessary  to  distil  under  reduced  pressure. 
The  material  from  the  ethereal  solution  was  purified  by  recrys- 
tallizing  from  a  little  alcohol.  It  then  formed  stout,  pointed 
prisms  and  the  melting-point  was  not  altered.  It  is  very  sol- 
uble in  ether,  alcohol,  and  petroleum  ether.  In  two  experi- 
ments, using  5  grams  of  the  methylmercaptobarbituric  acid, 
3.3  grams  and  3.4  grams  of  the  dichloride  were  obtained. 
The  yield  by  the  action  of  either  the  pentachloride  or  the  oxy- 
chloride  of  phosphorus,  especially  in  large  quantities,  was 
found  to  be  very  irregular.  A  nitrogen  determination  gave  : 

Calculated  for 
C5H4NsSCl2.  Found. 

N  I4-36  I4-76 

2-Methylmercapto-4.-chlor~6-aminopyrimidine, 

N=C— NH, 

I  I 

CH3SC  CH         .—Two  and  a  half  grams  of  the  2-methyl- 

II  il 
N CC1 

mercapto-4,6-dichlorpyrimidine  were  heated  in  a  sealed  tube 
with  about  75  cc.  of  alcoholic  ammonia  for  four  hours  at  125° 
to  126°.  On  cooling,  the  ammonium  chloride  which  had 
separated  was  filtered  and  the  filtrate  evaporated.  The  resi- 
due was  purified  by  recrystallizing  from  water,  in  which  it 
was  difficultly  soluble.  It  crystallized  in  colorless,  needle- 
like  prisms,  which  melted  at  127°  to  128°  to  a  colorless  liquid. 
A  yield  of  1.5  grams  of  purified  material  was  obtained.  Four 
other  experiments  gave  the  following  yields  : 

Chloride.  Monoamine. 

Grams.  Grains. 

3-7  2.6 

3-0  2.2 

3-2  2.7 

3-3  2.6 

A  nitrogen  determination  gave  : 

Calculated  for 
C6H6N3SC1.  Found. 

N  23.93  24.04 


348  Wheeler  and  Jamie  son. 

Action  of  Alcoholic  Ammonia. — This  chloraminopyrimidine 
(i.i  grams)  was  heated  with  about  75  cc.  of  alcoholic  ammo- 
nia (alcohol  saturated  with  dry  ammonia  at  o°)  at  145°  for 
three  hours  and  then  for  two  hours  at  150°,  whereupon  the 
material  was  recovered  completely  unaltered.  The  i.i  grams 
of  substance  were  reheated  with  the  same  volume  of  fresh  alco- 
holic ammonia  at  170°  for  two  hours,  and  then  at  190°  for  a 
half  hour  ;  0.7  gram  of  unaltered  material  was  obtained. 

Two  and  four-tenths  grams  of  the  chloraminopyrimidine 
were  heated  with  alcoholic  ammonia  for  two  hours  at  185°  to 
190°,  and  four  hours  at  215°  to  220°.  On  opening  the  tube 
the  alcohol  was  found  to  be  saturated  with  mercaptan.  A 
considerable  amount  of  a  light-yellow  precipitate  had  separa- 
ted from  the  alcohol.  This  was  filtered,  washed  with  alco- 
hol and  then  with  water.  It  melted  at  about  234°  to  240°  and 
it  gave  an  alkaline  reaction  to  turmeric  paper.  It  contained 
neither  sulphur  nor  chlorine  and  was  found  to  be  2,4,6-tri- 
aminopyrimidine,  which  has  been  described  by  Gabriel.1 

N=C— NH2 

4-Chlorcytosine,  OC  CH         . — This  was  obtained  by 

I          I! 
HN CC1 

boiling  0.5  gram  of  the  above  mercapto  derivative  with  con- 
centrated hydrochloric  acid.  Mercaptan  was  readily  evolved 
and  upon  evaporating  the  solution,  4-chlorcytosine  hydrochlo- 
ride  was  obtained.  This  crystallized  from  hot  water  in  balls 
of  very  small,  slender,  hard  prisms  or  needles.  From  dilute 
aqueous  solutions  of  this  salt,  ammonia  precipitates  a  crop  of 
flat,  colorless  prisms ;  from  more  concentrated  solutions  the 
base  separates  as  a  jelly  resembling  thick  starch  paste,  which 
is  difficult  to  filter.  When  dried  on  paper  it  adheres  strongly 
to  the  fiber.  It  is  fairly  soluble  in  water  and  it  does  not  melt 
at  300°,  although  it  sinters  and  gradually  turns  red.  A  nitro- 
gen determination  gave  : 

Calculated  for 
C4H4ON3C1.  Found. 

N  28.86  28.73 

1  Ber.  d.  chera.  Ges.,  34,  3364. 


2-  Oxy-4,6-diaminopyrimidine.  349 

The  chlorine  in  this  compound  is  very  firmly  bound.  It 
was  not  removed  by  tin  and  hydrochloric  acid,  or  by  red  phos- 
phorus and  hydriodic  acid. 

When  1.5  grams  of  this  material  were  heated  with  alcoholic 
ammonia  at  183°  for  two  hours  0.95  gram  of  substance  insol- 
uble in  alcoholic  ammonia  was  formed.  It  was  difficultly  sol- 
uble in  water ;  if  the  solution  was  cooled  rapidly,  very  small 
crystals  were  obtained  ;  if  slowly  cooled,  little  balls  were 
formed.  This  substance  did  not  melt  at  307°.  It  was  free 
from  chlorine  and  a  nitrogen  determination  gave  only  24.9 
per  cent  nitrogen.  It  was  not  identified,  "since  two  attempts 
to  prepare  the  compound  failed  on  account  of  the  explosion  of 
the  sealed  tubes  and  no  time  was  available  to  repeat  the  work. 

2-Methylmercapto-4.,6-diaminopyrimidine, 
Ni=z:C— NH2 

I  I 

CHSSC  CH         . — Malonic  nitrile  and  thiourea  were  con- 

II  II 

N C— NH8 

densed  according  to  Traube's1  directions  in  an  alcoholic  solu- 
tion with  sodium  ethylate.  Two  grams  of  the  2-thio-4,6-di- 
aminopyrimidine  were  moistened  with  alcohol  and  2.2  grams 
of  methyl  iodide  were  added.  The  mixture  stood  two  hours 
without  change.  Suddenly,  heat  was  evolved  and  the  solution 
solidified.  The  alcohol  was  evaporated  and  the  residue  was 
dissolved  in  water.  Ammonia  then  precipitated  2.2  grams  of 
colorless  crystalline  material.  This  was  quite  soluble  in  hot 
water,  from  which,  on  cooling,  it  separated  in  the  form  of 
slender  prisms.  It  melted  at  185°  to  186°  with  a  little  effer- 
vescence, and  a  nitrogen  determination  gave  : 

Calculated  for 
C6H8N4S. 

N  35-89 


2~Oxv-4,6-diaminopynmidinc,  OC  CH         . — One  gram 

HN 

1  Ann.  Chem.  (I<iebig),  331,  80  (1904). 


350  Wheeler  and  Jamie  son. 

of  the  2-methylmercapto-4,6-diaminopyrimidine  was  evapora- 
ted twice  with  about  20  cc.  of  concentrated  hydrochloric  acid 
on  the  steam-bath.  Methylmercaptan  was  evolved  and  the 
residue  crystallized  from  water.  The  monohydrochlo- 
ride  which  separated  formed  long,  slender  prisms  which  did 
not  melt  at  307°.  This  salt  was  dissolved  in  water  and  an 
excess  of  ammonium  hydroxide  was  added,  whereupon  a  fine 
crystalline  meal  was  precipitated.  It  was  difficultly  soluble 
in  hot  water,  and  it  separated  as  slender,  rectangular,  anhy- 
drous prisms.  When  the  material  was  heated  it  became 
gradually  yellow  at  about  297°  and  remained  a  dry,  yellow 
powder  at  347°.  A  nitrogen  determination  gave  : 

Calculated  for 

C4H6ON4.  Found. 

N  44.44  44.82 

The  picrate  separated  from  hot  water  when  slowly  cooled  in 
the  form  of  thin  tables.  If  rapidly  cooled  it  formed  bunches 
of  slender  prisms.  It  had  a  bright  yellow  color,  and  a  nitro- 
gen determination  showed  that  it  was  a  monopicrate  : 

Calculated  for 
C10H9O8N7.  Found. 

N  27.60  27.46 

It  sinters  at  about  185°  and  melts  with  effervescence  at  210° 
to  214°. 

It  was  found  that  if  the  2-methylmercapto-4,6-diamino- 
pyrimidine  was  warmed  with  hydrochloric  acid  for  a  longer 
time  than  was  sufficient  to  expel  the  mercaptan,  barbituric 
acid  was  obtained.  This  was  identified  by  its  crystallizing 
with  water  of  crystallization  and  by  the  following  nitrogen 
determination  in  the  dried  material  : 

Calculated  for 


N  21.89 

HN 

I 

2-Methylmercaptovioluric    Acid,    CHSSC  C=NOH.  - 

II  _  I 

Eight  grams  of  2-methylmercapto-4,6-dioxypyrimidine  were 


2-  Oxy-q.  ,  6-dia  minopyrimidine  .  35  1 

dissolved  in  150  cc.  of  water  containing  2  grams  of  sodium 
hydroxide.  Four  grams  of  sodium  nitrite  were  added  and 
the  solution  was  acidified  with  acetic  acid.  The  solution 
turned  dark-blue  when  acidified,  but  gradually  became  red. 
A  brick-red  precipitate  formed  after  the  solution  stood  ten 
hours  and  4.55  grams  of  the  isonitrosopyrimidine  were  ob- 
tained, or  48  per  cent  of  the  calculated.  It  became  dark-col- 
ored when  heated  and  gradually  decomposed  at  180°  to  200°. 
The  ammonium  and  sodium  salts  have  a  purple  color.  Some 
of  the  sodium  salt  was  dissolved  in  warm  water  and  acidified 
with  hydrochloric  acid.  The  solution  became  red,  and,  on 
standing,  it  deposited  red,  flat,  pointed  prisms,  which  con- 
tained 2  molecules  of  water  of  crystallization.  The  water 
was  determined  by  heating  the  material  at  120°. 

Calculated  for 
C5H6O8N3S.2H2O.  Found. 

H2O  u.66  11.84 

A  nitrogen  determination  in  the  case  of  the  anhydrous  ma- 
terial gave  : 

Calculated  for 


Found. 
N  22.46  22.22 

HN  --  CO 

I  I 
2-Methylmercaptouramil,  CH8SC           CHNH2.  —  This    was 

II  I 
N  -  CO 

obtained  from  the  above  isonitrosopyrimidine  by  reduction 
with  ammonium  sulphide  according  to  Traube's  method.1 
This  material  is  difficultly  soluble  in  water  or  hydrochloric 
acid,  dilute  or  concentrated.  It  is  soluble  in  sodium  hydrox- 
ide and  it  is  precipitated  by  acetic  acid,  in  which  it  is  diffi- 
cultly soluble.  A  nitrogen  determination  gave  : 

Calculated  for 
C5H7O2N3S.  Found. 

N  24.28  24.37 

Attempts  to  chlorinate  this  material  by  means   of   phos- 
phorus oxy  chloride  did  not  lead  to  a  smooth  result.     The 

1  Ann.  Chem.  (I^iebig),  331,  82  (1904). 


352  Wheeler  and  Jamie  son. 

material  turns  brown  on  heating  at  285°  but  does  not  melt  at 

3oi°. 

The  following  pyrimidine  derivatives  were  prepared  by  Dr. 
Henry  F.  Merriam  in  the  course  of  some  work  on  isomers  of 
histidine.  The  work  was  interrupted  by  the  departure  of 
Mr.  Merriatn  from  this  laboratory. 

HN CO 

2-  Thio-5-methylbarbituric  Acid,    SC  CHCH3. Seven 

I  I 

HN CO 

and  eight-tenths  grams  of  sodium  were  dissolved  in  alcohol 
and  the  solution  added  to  60  grams  of  methylmalonic  ethyl 
ester.  A  hot  alcoholic  solution  of  26  grams  of  thiourea  was 
then  added  and  the  mixture  heated  gently  on  the  steam-bath 
for  five  hours.  The  white  sodium  salt  was  then  filtered,  dis- 
solved in  a  small  volume  of  hot  water,  and  the  solution  acidi- 
fied strongly  with  hydrochloric  acid.  On  cooling,  a  mass  of 
thin  plates  separated.  After  crystallizing  from  water  the  sub- 
stance melted  with  effervescence  at  about  244.°  The  yield 
was  27  grams.  2-Thio-5-methylbarbituric  acid  crystallizes 
with  i  molecule  of  water  of  crystallization,  which  is  evolved 
at  120°. 

Calculated  for 
C5H6O2N2S.H2O.  Found. 

H2O  18.55  18.25 

A  nitrogen  determination  in  the  case  of  the  dried  material 
gave: 

Calculated  for 
C5HeO2N2S.  Found. 

N  I7-72  18.04 

2-  Tkio-5-ethylbarbituric  Acid. — An  alcoholic  solution  of  n 
grams  of  sodium  was  added  to  90  grams  of  ethylmalonic  ethyl 
ester  and  a  solution  of  37  grams  of  thiourea  in  hot  alcohol  was 
added  to  the  mixture,  which  was  then  warmed  on  the  steam- 
bath  for  several  hours.  The  white  sodium  salt  was  then  re- 
moved by  filtering  and  the  free  acid  was  liberated  by  means 
of  hydrochloric  acid.  It  separated  from  water  in  the  form  of 
long,  needle-like  prisms  and  it  melted  at  190°  to  191°.  It  is 


2-  Oxy-j.,  6-diaminopyrimidine.  353 

soluble  in  alcohol.  The  yield  was  37  grams.  It  contains 
water  of  crystallization,  which  is  given  off  at  120°.  A  nitro- 
gen determination  in  the  dry  material  gave  : 

Calculated  for 
C6H8O2N2S.  Found. 

N  16.27  16.53 

2-Methylmercapto-4, 6-dioxy-5-methylpyrimidine, 
HN CO 

I  I 

CH3SC  CHCH3.— This  compound  was  prepared  by  boil- 

II  I 
N CO 

ing  2-thio-5-methylbarbituric  acid  with  alcohol  and  an  excess 
of  methyl  iodide.  After  several  hours  the  solid  material  was 
filtered  and  washed  with  alcohol.  The  material  was  almost 
insoluble  in  water  and  alcohol  and  it  was  purified  by  crystal- 
lizing  from  strong  acetic  acid.  It  formed  short  prisms  which, 
on  heating,  decomposed  with  effervescence  at  about  303°. 
From  28  grams  of  thiomethylbarbituric  acid  18.5  grams  of 
the  mercapto  compound  were  obtained. 

Calculated  for 
C6H8O2N2S.  Found. 

N  16.27  16.23 

2-Methylmercapto-4,6~dioxy-5-ethylpyrimidine. Thirty-six 

grams  of  5-ethylthiobarbituric  acid,  treated  in  the  same  man- 
ner as  the  above,  except  that  in  this  case,  after  the  action  was 
complete,  most  of  the  alcohol  was  evaporated  and  the  residue 
was  treated  with  water,  gave  25  grams  of  the  mercapto  com- 
pound. After  crystallizing  from  acetic  acid  it  melted  with 
effervescence  at  about  257°.  It  was  easily  soluble  in  alcohol 
and  acetic  acid  and  difficultly  soluble  in  water.  A  nitrogen 
determination  gave  : 

Calculated  for 
C7Hi0O2N2S.  Found. 

N  15.05  15.19 

2'Methylmercapto-^. ,  6-dichlor-5~methylpyrimidinc, 
N:=CC1 

I  I 

CH8SC  CCH,.— Ten  and  three-tenths  grams  of  2-methyl- 

II  II 
N CC1 


354  Wheeler  and  Jamieson. 

mercapto-4,6-dioxy-5-methylpyrimidine  were  heated  on  the 
steam-bath  with  12.7  grams  of  phosphorus  pentachloride. 
The  material  melted  and,  finally,  the  phosphorus  oxychloride 
was  removed  by  distilling  in  a  vacuum.  The  residue  was 
treated  with  ice- water  and  ether  and  the  ethereal  solution  was 
dehydrated  and  distilled  at  18  mm.  pressure.  The  dichloride 
then  boiled  at  153°  to  154°,  and,  on  coolin'g,  it  crystallized  in 
the  form  of  colorless,  stout  prisms  melting  at  64°.  The  yield 
was  10.3  grams  and  a  nitrogen  determination  gave  : 

Calculated  for 
C6H6N2SC12.  Found. 

N  13.39  13.48 

As  in  the  case  of  2-methylmercapto-4,6-dichlorpyrimidine, 
only  one  chlorine  atom  is  especially  reactive  in  this  com- 
pound. 

2-Methylmercapto-4.-chlor~5-methyl-6-ethoxypyrimidine, 
N=COC3H5 

i  I 

CH3SC  CCH3     . — Seven  grams  of  the  above  dichloride 

II  II 

N CC1 

were  dissolved  in  alcohol  and  0.9  gram  of  sodium  in  alcoholic 
solution  was  added.  The  mixture  was  warmed  for  an  hour 
on  the  steam-bath.  The  material  was  then  precipitated  with 
water  and  crystallized  from  alcohol,  whereupon  beautiful, 
colorless  prisms  were  obtained  melting  at  85°.  This  sub- 
stance is  readily  soluble  in  alcohol  and  benzene  and  insoluble 
in  water.  The  yield  was  6  grams.  A  nitrogen  determina- 
tion gave  : 

Calculated  for 

C8HUON2SC1.  Found. 

N  12. 81  13.18 

2-Methylmercapto-4-chlor-5-methyl-6-methylaminopyrimidine, 
Nzz=C— NHCH. 

I  I 

CH3SC  CCH3  .—Nine  grams  of  the  above  dichlor 

il         II 

N CC1 

compound  were  heated  at  145°,  for  three  hours,  with  5  grams 


2-  Oxy-  4. ,  6-diaminopyrimidine.  355 

of  methylamine  in  58  cc.  of  alcohol.  The  solution  was  then 
evaporated,  the  residue  washed  with  water  and  crystallized 
several  times  from  alcohol.  It  formed  stout  prisms,  which 
melted  at  157°.  The  reaction  was  not  complete  and  the  yield 
was  5  grams.  A  nitrogen  determination  gave  : 

Calculated  for 
C7H10N3C1S.  Found. 


N  20.64  20.96 


5'Dimethylaminouracil,  OC  C — N(CH3)2.  —  This  com- 


HN CH 

pound,  isomeric  with  histidine,  was  prepared  by  heating 
5-bromuracil1  with  an  excess  of  dimethylamine  at  150°  for  six 
hours.  The  contents  of  the  tube  were  evaporated,  taken  up 
in  water,  and  boiled  with  animal  charcoal.  The  material  was 
then  crystallized  from  water,  in  which  it  is  moderately  soluble 
when  hot,  and  very  difficultly  soluble  when  cold.  It  formed 
small,  thin,  colorless  plates  or  films,  which  melted  with  strong 
effervescence  at  about  297°.  A  nitrogen  determination  gave  : 

Calculated  for 

CaHeOsNs.  Found. 

N  27.09  27.23 

HN CO 

I  I 

4-Methyl-5-methylaminouracil,  OC  C— NHCH3.  —  Fif- 

I  II 

HN CCH8 

teen  grams  of  4-methyl-5-bromuracil,  prepared  according  to 
the  directions  of  Behrend,"  were  heated  for  six  hours  at  150* 
with  an  excess  of  aqueous  methylamine.  The  contents  of  the 
tube  were  then  heated  on  the  steam-bath  until  the  free 
methylamine  was  removed.  The  bromine  was  removed  by 
means  of  silver  sulphate,  the  excess  of  silver  by  hydrogen 
sulphide,  and  the  sulphuric  acid  by  barium  hydroxide,  and 
the  excess  of  the  latter  was  precipitated  by  carbon  dioxide. 
Then,  on  concentrating  the  solution  to  a  small  volume,  a 

1  Wheeler  and  Merriam  :  This  JOURNAL,  39,  486  (1903). 

2  Ann.  Chem.  (Liebig),  231,  249. 


356  Wheeler  and  Jamie  son. 

beautiful  crop  of  colorless  prisms  separated.  After  crystal- 
lizing from  water  containing  a  little  alcohol  the  compound 
melted  at  214°.  When  crystallized  from  water,  in  which  it  is 
very  soluble,  it  contains  i  molecule  of  water  of  crystallization. 
The  presence  of  much  alcohol  in  the  water  causes  the  com- 
pound to  crystallize  in  an  anhydrous  condition.  Water  was 
determined  by  heating  the  material  at  120°. 

Calculated  for 

CeHgOijNg.H^O.  Found. 

H3O  10.40  10.26 

A  nitrogen  determination  in  the  case  of  the  dried  material 
gave  : 

Calculated  for 
CflHgOaNs.  Found. 

N  27.09  27.25 

The  monohydrochloride  was  prepared  by  dissolving  the  base 
in  dilute  hydrochloric  acid  and  evaporating  the  solution.  It 
formed  beautiful,  transparent,  stout  prisms,  which  melted  at 
273°  with  strong  effervescence.  The  hydrochloride  was  less 
soluble  in  water  than  the  free  base,  and  the  following  analy- 
sis showed  that  the  salt  was  anhydrous  : 

Calculated  for 

CeHeOjNg.HCl.  Found. 

N  21.93  22.27 

2-Methylmercapto-4. ,  6-dimethylpyrimidine , 
N CCH, 

II  II 

CH8SC  CH8    .— (ByG.  SJamieson.)    Thirty-five  grams 

N=CCH8 

of  the  methyl  iodide  addition-product  of  thiourea  were  dis- 
solved in  30  cc.  of  water  containing  9  grams  of  potassium  hy- 
droxide and  1 6  grams  of  acetylacetone  were  then  added. 
The  latter  dissolved  when  the  solution  was  shaken  vigorously 
for  a  few  seconds.  The  clear  solution  gradually  became  tur- 
bid, and,  after  standing  for  two  days,  a  dark-yellow  oil  sepa- 
rated. This  was  shaken  out  with  ether  and  the  ethereal  solu- 
tion was  dehydrated  over  potassium  hydroxide.  The  oil  was 
then  distilled  at  28  to  29  mm.  pressure,  whereupon  it  boiled 


2-Oxy~4,6  diaminopyrimidine .  357 

at  135°  to  137°,  leaving  a  notable  residue.  Six  grams  of  col- 
orless, odorless  oil  were  obtained,  a  yield  of  24.4  per  cent  of 
the  calculated.  Another  condensation  was  made  with  three 
times  the  above  quantities  and  17.7  grams  of  oil  were  ob- 
tained which  boiled  at  144°  at  33  mm.  pressure  and  at  123°  to 
125°  at  14  mm.  pressure.  The  yield  in  this  case  was  23.9  per 
cent  of  the  calculated.  When  the  oil  was  cooled  it  solidified 
to  a  white,  ice-like  mass  and  melted  at  about  23°  to  24°.  The 
material  is  moderately  soluble  in  cold  water,  and  when  the 
solution  is  warmed  the  substance  separates  in  the  form  of  oil 
drops,  which  dissolve  again  on  cooling.  It  appears  to  absorb 
moisture  from  the  air,  since  only  by  drying  over  sulphuric 
acid  could  agreeing  results  be  obtained  on  analysis.  Nitro- 
gen determinations  then  gave : 

Calculated  for  Found. 

C7H10N2S.  I.  II. 

N  18.18  18.22  18.32 

The  residue,  obtained  as  a  by-product  in  this  preparation, 
was  not  distilled,  but  when  crystallized  from  alcohol,  in  which 
it  was  very  soluble,  it  separated  in  the  form  of  colorless,  rec- 
tangular prisms,  which  melted  at  153°  to  154°  to  a  clear 
liquid.  A  nitrogen  determination  agreed  with  the  calculated 
for  a  dic)7'andiamide  addition-product  of  2-methylmercapto- 
4,6-dimethylpyrimidine  or  an  isomer.  It  was  not  further  ex- 
amined. 

2-Oxy-4.,6-dimethylpyrimidine. — The  above  mercapto  deriv- 
ative, melting  at  23°  to  24°,  was  boiled  with  hydrobromic  acid 
for  three  hours,  evaporated,  taken  up  in  water,  and  neutral- 
ized with  alkali.  It  was  again  evaporated  and  the  dried, 
powdered  material  was  extracted  with  benzene  containing 
alcohol.  The  extracted  material  was  crystallized  twice  from 
water,  in  which  it  was  easily  soluble.  It  melted  at  198°  to 
199°.  Kvans1  gives  the  melting-point  of  this  substance,  which 
he  prepared  by  a  different  method,  at  190°  to  195°.  Our  ma- 
terial was  shown  to  be  identical  with  that  of  Evans  by  pre- 
paring the  bromine  derivative  melting  at  145°  and  by  its  be- 
havior with  diazobenzene  chloride. 

NEW  HAVEN,  CONN.,  June,  1904. 
1  J.  prakt.  Chem.,  48,  489  (1893). 


[Reprinted  from  the  American  Chemical  Journal.    Vol.  XXXIII,  No.  5. 
May,  1905.] 


Contributions  from  the  Sheffield  Laboratory  of  Yale  University. 

CXXII.  —  RESEARCHES     ON     PYRIMIDINES  :      THE 
STRUCTURE  OF  SOME  SUBSTITUTION- 
PRODUCTS. 

[EIGHTH  PAPER.] 

BY  HENRY  I,.  WHEELER  AND  H.  STANLEY  BRISTOL. 

When  a  pyrimidine  derivative,  having  hydrogen  both  in  the 
4-  and  5-positions,  is  attacked  by  the  halogens  or  nitric  acid, 
the  question  as  to  which  hydrogen  atom  is  replaced  or  substi- 
tuted has  not,  hitherto,  been  decided.  A  method,  which  has 
now  been  successful  in  dealing  with  this  question,  depends  on 
the  structure  of  Behrend's  nitro-  and  aminouracil.  Nitro- 
uracil  has  the  nitro  group  in  the  5-position,  as  it  is  prepared 
from  4-methyluracil,1  (I.),  or  5-nitrouracil-4-carboxylic  acid2, 
(II.): 

HN CO  HN CO  HN CO 

II  II  II 

OC         CH        —     OC         CNO2        ~     OC         CNO2 

II                         I           II                            I  II 

HN CCHS  HN CCO2H  HN CH 

I.  II.  in. 

1  Kohler:  Ann.  Chem.  (Liebig),  236,  50  (1886). 

2  Behrcnd  :  Ibid.,  229,  36  (1885)  ;  240,  5  (1887). 


Wheeler  and  Bristol. 

Aminouracil  results  by  reduction  of  the  above  nitrouracil, 
the  ammo  group  is,  therefore,  in  the  5-position.  Neither  nitro- 
uracil nor  aminouracil  has  a  definite  melting  or  decomposing 
point.  5-Aminouracil  picrate,  however,  has  a  definite  effer- 
vescing point,  which  serves  to  identify  it.  Behrend  and  Griin- 
wald1  state  that  this  compound  melts  at  I47°-I48°.  This  is 
incorrect,  possibly  a  typographical  error.  It  has  been  found, 
by  several  workers  in  this  laboratory,  that  the  action  of  nitric 
action  on  uracil,  2-ethylmercapto-6-oxypyrimidine,  2-thiouracil 
and  other  pyrimidine  derivatives  leads  to  the  formation  of  a 
nitrouracil.  In  each  case,  after  reduction  with  aluminium 
amalgam,  the  product  gave  a  picrate  effervescing  sharply  at 
247°,  or  100°  higher  than  the  temperature  given  by  the  above 
authors.  At  the  request  of  one  of  us,  Mr.  C.  O.  Johns  pre- 
pared 5-nitrouracil  (III.)  by  Behrends'  method  and  this,  on  re- 
duction, gave  a  picrate  showing  no  signs  of  melting  at  147°  but 
effervesced,  as  in  the  other  cases,  at  247°.  The  compounds 
were  identical  and  it  therefore  follows  that  nitric  acid  attacks 
these  various  pyrimidine  derivatives  in  the  5-position. 

For  the  purpose  of  comparison,  Traube's  2,6-dioxy-4-amino- 
pyrimidine  or  4-aminouracil2  was  prepared.  When  the  satura- 
ted aqueous  solution  of  this  substance  was  mixed  with  a  satu- 
rated solution  of  picric  acid  no  precipitate  resulted  and  no 
picrate  was  obtained. 

It  was  stated  in  a  previous  article8  that  Dr.  Merriam  ob- 
tained 5-aminouracil  when  the  product,  obtained  by  bromina- 
ting  uracil,  was  heated  with  aqueous  ammonia  at  180°  ;  it  was 
identified  by  means  of  its  picrate.  A  specimen  of  the  picrate, 
prepared  by  Dr.  Merriam,  was  found,  by  us,  to  sinter  decidedly 
about  147°,  but  did  not  melt,  or  rather  effervesce,  until  247°. 
The  compound  proved  to  be  identical  with  the  above  products 
and  it  therefore  follows  that  bromine  attacks  uracil  in  the 
5-position,  as  previously  represented. 

It  might  be  expected  that  a  2-alkylmercapto-6-oxypyrimi- 
dine  would  also  give  a  5-brom  derivative.  This  was  proved  to 
be  the  case  as  follows  :  5-Bromuracil  (IV. )  was  converted  into 

1  Ann.  Chem.  (Liebig),  309,  259  (1899). 
8  Ber.  d.  chem.  Ges.,  33,  1381  (1900). 
3  THIS  JOURNAL,  31,  6031(1904). 


Researches  on  Pyrimidines  .  439 

2,6-dichlor-5-brompyrimidine  (V.)  by  warming  with  a  mix- 
ture of  phosphorus  oxychloride  and  phosphorus  pentachloride 
and  this,   with   aniline,    gave   2,6-dianilino-5-brompyrimidine 
(VI.)  : 
HN  -  CO  N=CC1  N=C—  NHC6H5 


CBr  —   C1C         CBr   —    C6H5NHC          CBr 


N CH  N CH 

V.  VI. 

2-Ethylmercapto-6-oxypyrimidine  was  treated  with  bromine, 
in  glacial  acetic  acid  and  the  resulting  brom  derivative  (VII.) 
was  warmed  with  aniline  ;  this  gave  2-amlino-5-brom-6-oxy- 
pyrimidine  (VIII.)»  which  was  then  converted  into  the  chlo- 
ride (IX.).  When  this  chloride  was  warmed  with  aniline  the 
product  was  found  to  be  identical  with  the  above  dianilino- 
brompyrimidine  (VI.),  so  that  the  process  can  be  represented 
as  follows : 

CO  HN CO  N=C-C1 

I  II  II 

CBr  —  C6H5NHC         CBr  —  C6H5NHC         CBr 

II  II 

N CH 

VIII. 

Our  first  plan  of  procedure  for  deciding  the  question  of  the 
position  of  bromine  in  the  mercaptooxypyrimidines,  was  to  boil 
these  products  with  hydrochloric  acid  and  identify  the  brom- 
uracil  formed.  It  was  found,  however,  that  prolonged  boiling 
of  2-ethylmercapto-5-brom-6-oxypyrimidine  with  hydrochloric 
acid  gave  uracil,  the  bromine  being  entirely  removed.  The 
5-brom  derivatives  of  uracil  part  with  their  halogen  more  read- 
ily than  those  of  cytosine  or,  in  other  words,  an  oxygen  in  the 
6-position  renders  bromine  in  the  5-position  more  active  than 
when  the  6-position  is  occupied  by  an  amino  group.  This  is 
true  not  only  for  the  replacement  of  bromine  by  hydrogen,  but 
also  by  the  amino  group. 

We  have  found  that  2-ethylmercapto-4-ethyl-.5-brom-6-oxy- 
pyrimidine  (XI.)  also  loses  bromine  by  simply  evaporating  its 
solution,  in  concentrated  hydrochloric  acid,  to  dryness  on  the 


44-Q  Wheeler  and  Bristol. 

water-bath,  the  product  obtained  being  4-ethyluracil  (XII.). 
The  2-ethylmercapto-4-ethyl-6-oxypyrimidine  (X.)  for  this 
experiment  was  prepared  by  the  condensation  of  the  ethyl 
bromide  addition-product  of  thiourea  and  ethylpropionylacetate, 
CH3CH2COCH,CO.OCaH5,1  in  alkaline  solution. 

NH— CO  HN CO  HN CO 

II  III 

C2H6SC        CH        -+   C2H5SC         CBr       ^   OC         CH 

II          II  II          II  I  II 

N CC2H6  N CC2H5         HN CC2H5 

X-  XI.  XII. 

Bromine  is  represented  in  XI.  as  entering  at  the  5-position  and 
not  in  the  alkyl  group.  Behrend2  has  shown  that  when 
4-methyluracil  is  brominated  and  then  oxidized  bromuracil- 
carboxylic  acid  results. 

EXPERIMENTAL. 

The  uracil  used  in  this  work  was  prepared  by  boiling  various 
2-alkylmercapto-6-oxypyrimidines  with  concentrated  hydro- 
chloric acid.  In  the  course  of  our  experiments  a  number  of 
new  pseudoureas  and  alkylmercapto  pyrimidines  were  em- 
ployed. The  former  were  prepared,  for  analysis,  by  treating 
pure,  finely-powdered  thiourea  with  a  little  alcohol  and  the 
alkyl  halide  was  added.  The  mixtures  were  warmed  on  the 
steam-bath  until  solution  took  place  and  allowed  to  crystallize, 
in  a  vacuum,  over  sulphuric  acid.  The  crystals  were  then 
simply  washed  with  ether  ;  they  were  readily  soluble  in  water 
and  alcohol  and  insoluble  in  benzene  and  ether.  It  was  found 
that  pseudoethylthiourea  hydrobromide  dissolved  in  acetone, 
it  was  readily  soluble  in  pyridine  and  it  could  be  crystallized 
from  acetic  anhydride. 

Pseudonormalpropylthiourea  hydrobromide  formed  long,  color- 
less needles,  which  melted  at  about  60°. 

Calculated  for 

C4H14N2S.HBr.  Found. 

N  14-07  I4-I9 

Pseudoisobutylthiourea  hydrobromide  formed  a  fibrous  mass  of 
crystals,  melting  at  about  96°. 

1  Blaise  :  Compt.  rend.,  133,  978  (1901). 

2  Ann.  Chem.  (I^iebig),  240,  22  (1887). 


Researches  on  Pyrimidines.  441 

Calculated  for 

C5H12N2S.HBr.  Found. 

N  13.14  13.21 

Pseudoisoamylthiourea  hydrobromide  crystallized  in  long 
prisms,  melting  at  about  84°. 

Calculated  for 

C6H14N2S.HBr.  Found. 

N  I2-33  12.28 

HN CO 

I  I 
2-Normalpropylmercapto-6-oxypyrimidine,  C3H7SC         CH. — 

II  II 
N CH 

This  and  the  following  alkylmercaptooxypyrimidines  were 
prepared  by  the  method  described  in  the  case  of  the  corre- 
sponding ethyl  derivative.1  The  product  from  the  condensa- 
tion of  20  grams  of  the  normalpropylbromide  addition-product 
of  thiourea,  30  grams  of  ethyl  sodium  formylacetate  and  6 
grams  of  sodium  hydroxide,  amounted  to  12  grams.  It  was 
readily  soluble  in  alcohol  and  hot  water.  From  40  per  cent 
alcohol  it  formed  long,  colorless  needles,  melting  at  117°. 

Calculated  for 
C7H10ON2S.  Found. 

N  16.47  16.39 

2-Isobutylmercapto-6-oxypyrimidine. — Twenty-one  grams  of 
the  above  pseudoisobutylthiourea  hydrobromide,  38  grams  of 
ethyl  sodium  formyl  acetate  and  4  grams  of  sodium  hydroxide 
gave  about  12  grams  of  this  mercaptooxypyrimidine.  When 
crystallized  from  50  per  cent  alcohol  it  formed  leaf-like  plates, 
melting  at  107°. 

Calculated  for 
C8Hi2ON2S.  Found. 

N  15.21  15.19 

2-Isoamylmercapto-6-oxypyrimidine  crystallized  from  50  per 
cent  alcohol  in  long,  thin  plates,  melting  at  115°. 

Calculated  for 
C9Hi4ON2S.  Found. 

N  14.14  14.08 

Nitration  of  Uracil  (By  Mr.  S.  H.  Clapp). — One  gram  of 
uracil  was  added  to  a  mixture  of  5  cc.  of  concentrated  sul- 

1  THIS  JOURNAL,  39,  483  (1903). 


442  Wheeler  and  Bristol. 

phuric  acid  and  10  cc.  of  fuming  nitric  acid.  The  mixture 
was  heated  to  about  125°,  in  an  oil-bath,  for  an  hour.  On 
pouring  into  ice-water,  nitrouracil  separated  in  colorless,  pris- 
matic needles.  The  yield  was  about  i  gram.  This  compound 
was  reduced  by  means  of  aluminium  amalgam,  in  ammoniacal 
solution.  On  filtering  and  concentrating,  aminouracil  separa- 
ted in  balls  of  needles,  which  were  recrystallized  from  water ; 
they  gave  33.47  per  cent  of  nitrogen,  the  calculated  being 
33.07. 

^-Aminouracil  Pier  ate. — The  above  aminouracil  was  dissolved 
in  warm  water  and  a  hot  solution  of  picric  acid  was  added,  the 
picrate  then  separated  in  the  form  of  yellow,  rectangular 
plates  which  began  to  sinter  strongly  at  150°,  then  melted, 
with  effervescence,  at  247°-248°. 

Calculated  for 
C10H8O9N5.  Found. 

N  23.59  23.27 

Nitration  of  2-Ethylmercapto-6-oxypyrimidine. — 2-Ethylmer- 
capto-6-oxypyrimidine  can  be  dissolved  in  a  mixture  of  fum- 
ing nitric  acid  and  concentrated  sulphuric  acid,  at  the  ordinary 
temperature  and  be  recovered,  unaltered,  on  pouring  into  ice- 
water  and  neutralizing  with  sodium  carbonate.  If  the  mixture 
is  warmed  on  the  steam-bath  until  the  reaction  is  well  started, 
then  allowed  to  stand  in  a  warm  place  (about  60°),  large  crys- 
tals of  nitrouracil  separate. 

The  following  was  found  to  be  the  easiest  method  of  pre- 
paring nitrouracil :  Ten  grams  of  2-ethylmercapto-6-oxy- 
pyrimidine  were  dissolved  in  a  mixture  of  20  cc.  of  red,  fum- 
ing nitric  acid,  10  cc.  of  concentrated  nitric  acid  and  10  cc.  of 
concentrated  sulphuric  acid.  The  reaction  was  started  by 
warming  on  the  steam-bath,  then  the  liquid  was  allowed  to 
stand,  at  about  60°,  for  several  hours,  4.9  grams  of  well-crys- 
tallized nitrouracil  separated.  The  crystals  were  filtered  and 
the  acid  filtrate  allowed  to  stand  for  24  hours  longer,  at  60°, 
whereupon  2.7  grams  of  nitrouracil  separated,  or  7.6  grams  in 
all.  This  is  a  yield  of  75.5  per  cent  of  the  calculated.  When 
the  compound  was  reduced  by  means  of  aluminium  amalgam 
and  the  picrate  prepared,  it  was  found  that  the  latter  became 


Researches  on  Pyrimidines.  443 

black  at  about  190°,  but  nevertheless  effervesced  sharply  at 
247°.  The  same  partial  decomposition  and  effervescing  point 
was  noticed  in  the  case  of  the  picrate  prepared  in  the  following 
experiment. 

Nitration  of  2-Thio-6-oxypyrimidine.  —  Twenty-five  per  cent 
nitric  acid  reacts  energetically  with  this  pyrimidine  derivative 
and  a  portion  is  converted  into  nitrouracil.  Eight  grams  of 
2-thiouracil  gave  about  4  grams  nitrouracil  ;  beside  this  a  far 
more  soluble  substance  was  formed,  which  gave  a  bulky  pre- 
cipitate with  mercuric  chloride,  it  was  probably  6-oxypyrimi- 
dine,  but  was  not  isolated. 

Nitration  of  2-Ethylmercapto-6-chlorpyrimidine  (By  Dr.  T.  B. 
Johnson).  —  The  mercaptochlorpyrimidine  (1.5  grams)  was 
added  to  a  mixture  of  4  cc.  of  concentrated  nitric  acid  and  4 
cc.  of  concentrated  sulphuric  acid.  The  temperature  of  the 
mixture  was  not  allowed  to  rise  above  90°;  it  was  maintained 
at  this  point  until  effervescence  ceased.  The  product  was 
cooled,  poured  on  to  ice  and  crystallized  from  water  ;  it  con- 
tained 27.1  per  cent  nitrogen,  the  calculated  percentage  for 
nitrouracil  is  26.7.  This  substance  was  reduced  and  the 
picrate  prepared;  it  melted  or  effervesced  at  247°. 


I 
C 


2,6-Dichlor-^-brompyrimidine,  C1C         CBr.  —  Eleven    grams 

II  II 

N  -  CH 

of  5-bromuracil,  13  grams  of  phosphorus  pentachloride  and  40 
cc.  of  phosphorus  oxychloride  were  mixed  and  warmed  on  the 
steam-bath.  Hydrogen  chloride  was  evolved  and,  after  4 
days,  all  of  the  bromuracil  dissolved.  The  solution  was  poured 
on  to  ice  and  extracted  with  ether.  The  ether  was  dried  over 
calcium  chloride  and  evaporated,  leaving  8  grams  of  oil,  which 
boiled  at  H9°-i2o°  (17-18  mm.).  It  solidified,  in  a  freezing- 
mixture,  to  a  crystalline  mass  and  melted  at  —  3°  --  2°. 

Calculated  for 
C4HN2Cl2Br.  Found. 

N  12.28  12.46 


444  Wheeler  and  Bristol. 

2,6-Dianilino-5-bromyprimidine, 
T3==C— NHC6H6 

C6H,NH— C          CBr  .—Six    grams    of  2,6-dichlor-5- 

II  II 

N CH 

brompyrimidine  were  mixed  with  10  grams  of  aniline,  heat  was 
evolved  and  the  mass  solidified  to  a  hard  cake.  This  was 
powdered  and  boiled  with  benzene,  the  benzene  and  aniline 
were  removed  by  a  current  of  steam  and  the  insoluble  material 
was  crystallized  from  alcohol.  It  formed  a  felted  mass  of 
colorless  needles,  difficultly  soluble  in  water,  which  melted  to 
a  clear  oil  at  191°. 

Calculated  for 

Ci6H13N4Br. 

N  16.42 

HN- 

I 
2-  A  nilino-j-brom-d-oxypynmidine,      C6H5NH  C 

II 
N CH 

Five  grams  of  2-ethylmercapto-5-brom-6-oxypyrimidine  were 
heated  with  excess  of  aniline  on  the  steam- bath,  until  the  odor 
of  mercaptan  disappeared  (24  hours).  At  first  solution  took 
place,  then  crystalline  material  separated.  The  product,  after 
washing  with  cold  alcohol,  was  free  from  sulphur  and  weighed 
about  6  grams.  It  was  difficultly  soluble  in  water,  alcohol, 
benzene  and  acetone.  From  alcohol  it  separated  in  the  form 
of  colorless,  needle-like  prisms,  melting  at  246°  with  effer- 
vescence. 

Calculated  for 

Ci0H8ON8Br.  Found. 

N  15.78  16.11 

N=  =CC1 

I  I 
2-Anilino-5-brom-6-chlorpyrimidine,    C6H6NHC          CBr.  — 

II  II 
N CH 

The  above  anilinobromoxypyrimidine  (4.7  grams)  was  di- 
gested on  the  steam-bath  with  phosphorus  oxychloride  until 
solution  took  place  and  hydrogen  chloride  ceased  being 


Researches  on  Pyrimidines.  445 

evolved.  It  was  then  poured  on  to  ice  and  the  solid  that  sepa- 
rated was  extracted  with  ether.  It  was  readily  soluble  in 
ether  and  benzene  and  crystallized  from  ligroin  in  bunches  of 
long,  radiating,  colorless  needles  which  melted,  to  a  clear  oil, 
at  io6°-io7°. 

Calculated  for 

Ci0H7N8ClBr.  Found. 

N  14.76  14.45 

A  small  quantity  of  this  compound  was  warmed  with  excess 
of  aniline  on  the  steam-bath,  the  mixture  liquefied  and  in  a  few 
minutes  solidified  to  a  hard  cake.  On  crystallizing  from  alco- 
hol it  gave  a  felted  mass  of  needles,  melting  at  191°  and,  when 
mixed  with  2,6-dianilino-5-brompyrimidine,  described  above, 
the  melting-point  was  not  altered. 

HN CO 

2-Ethylmercapto-4.-ethyl-6-oxypyrimidine,  C2H5SC         CH 

ii      ii 

N CC,H5 

— A  solution  of  5.7  grams  of  sodium  hydroxide,  12.5  grams  of 
pseudoethylthiourea  hydrobromide  and  10  grams  of  ethyl  pro- 
pionyl  acetate  was  made  in  25  cc.  of  water,  the  constituents  be- 
ing added  in  the  order  named.  The  mixture  was  allowed  to 
stand  for  a  number  of  hours,  then  warmed  and,  on  cooling,  it 
was  acidified  with  acetic  acid.  An  oil  separated  which  finally 
solidified,  and,  after  washing  and  drying,  weighed  about  6 
grams.  It  dissolved,  with  difficulty,  in  hot  water,  giving  col- 
orless, truncated  pyramids.  From  alcohol,  in  which  it  is  very 
soluble,  it  crystallized  in  large,  stout,  transparent  prisms, 
which  melted  at  89°  without  decomposition. 

Calculated  for 
C8H12ON2S.  Found. 

N  15.21  15.13 

2-Ethylmercapto-4.-ethyl-5-brom-6-oxypyrimid'ine, 
HN CO 

C2H5SC         CBr     . — Six  grams  of  the  above  crude  product 

II          II 
N CC2H5 

were  dissolved  in  8  grams  of  glacial  acetic  acid  and  a  slight  ex- 


446  Wheeler  and  Bristol. 

cess  of  bromine  added.  A  mass  of  six-sided  plates  separated 
and  more  was  obtained  on  diluting  with  water.  The  yield  of 
crude  material  was  a  little  over  6  grams.  When  crystallized 
from  alcohol  it  formed  large,  stout,  colorless,  transparent 
prisms  and  melted,  to  a  clear  liquid,  at  172°-! 73°. 5. 

Calculated  for 

C8HuON2SBr.  Found. 

N  10.64  10.64 

HN CO 

4-Ethyluracil,    OC          CH     . — The    above    mercaptobrom- 

I  II 

HN CC2H5 

pyrimidine  dissolves  in  concentrated  hydrochloric  acid  but  is 
precipitated  again  by  adding  water.  It  was  digested  on  the 
steam-bath,  with  strong  hydrochloric  acid,  for  some  time  and 
then  evaporated  to  dryness.  The  residue  was  more  readily 
soluble  in  water  than  in  alcohol.  When  crystallized  from  the 
latter  it  formed  beautiful,  colorless  tables  or  blocks,  which 
melted  at  204°  .to  a  clear  liquid;  it  effervesced  at  about  270°. 

Calculated  for 
C6H8O2N2.  Found. 

N  2O.O  20.2 

The  same  product  was  obtained  by  boiling  2-ethylmercapto- 
4-ethyl-6-oxypyrimidine,  melting  at  89°,  with  hydrochloric 
acid. 

HN CO 

I  I 

4-Ethyl-5-bromuracil,    OC         CBr     .—The   above  4-ethyl- 

HN CC2H5 

uracil  was  dissolved  in  glacial  acetic  acid,  in  which  it  is  not 
very  soluble  and  a  slight  excess  of  bromine  was  added.  On 
cooling,  very  thin,  oblong  plates  separated.  These  were  diffi- 
cultly soluble  in  hot  water  and  crystallized,  when  slowly 
cooled,  in  long,  thin,  snow-white,  glistening  prisms  that  were 
highly  etched.  The  material  crystallized  from  alcohol  in 
plates,  or  from  strong  solution  in  wisps.  At  23o°-23i°  it 
melted  to  a  yellow  liquid,  which  immediately  turned  brown 
and  then  effervesced. 


Researches  on  Pyrimidines.  447 

Calculated  for 
C6H7O2N2Br.  Found. 

N  12.78  12.62 

2-Methylmercapto-6-oxypyrimidine  Hydrochloride.  —  This  was 
obtained  on  passing  chlorine  into  a  glacial  acetic  acid  solution 
of  the  mercaptoxypyrimidine  and  precipitating  with  ether.  It 
was  crystallized  from  glacial  acetic  acid  and  formed  prismatic 
plates,  which  were  washed  with  ether.  It  was  very  soluble  in 
alcohol  and  water,  the  aqueous  solution  giving  a  strong  odor 
of  mercaptan.  When  boiled  with  hydrochloric  acid,  uracil 
was  obtained.  It  melted,  with  vigorous  effervescence,  at  189°. 

Calculated  for 


Found. 

N  15.7  15.8 

N  -  CC1 

2-Methylmercapto-6-chlorpyrimidine,  CH3SC  CH  .-When 


the  above  hydrochloride  (32  grams)  was  warmed  with  the  cal- 
culated quantity  of  phosphorus  pentachloride  and  some  phos- 
phorus oxychloride,  it  dissolved  and  hydrogen  chloride  was 
given  off.  The  solution  was  poured  on  to  ice  and  extracted 
with  ether,  dried  and  distilled  (36  mm.).  The  colorless  oil 
boiled,  for  the  most  part,  at  I39°-I4O°  ;  on  cooling  in  a  freez- 
ing mixture  it  solidified  and  melted  at  about  — 2° — o°. 

Calculated  for 
C5H5N2SC1.  Found. 

N  17.4  16.9 

N=C— NH2 

2-Methylmercapto-6-aminopyrimidine,  CH3SC          CH        . — 

II  II 

N CH 

The  above  chloride  was  heated  with  a  large  excess  of  concentrated 
alcoholic  ammonia,  at  I2o°-i3o°,  for  3  hours.  The  ammonium 
chloride  that  separated  was  filtered  and  the  filtrate  evaporated 
to  dryness.  The  residue  was  treated  with  water,  dried  and 
crystallized  from  benzene.  It  formed  large,  colorless,  diamond- 
shaped,  prismatic  plates  which  melted,  to  a  clear  oil,  at  125°- 


448  Wheeler  and  Bristol. 

126°.     It  was  readily  soluble  in  alcohol  and  acetone,  insoluble 
in  ether  and  ligroin. 

Calculated  for 

CfiH7NsS.  Found. 

N  29.79  29.76 

NBW  HAVEN,  CONN., 
January,  1905. 


[Reprinted  from  the  American  Chemical  Journal.     Vol.  XXXIII,  No.  5. 
May,  1905.] 


Contributions  from  the  Sheffield  Laboratory  of  Yale  University. 

CXXIII.  —  RESEARCHES    ON     PYRIMIDINES  :    THE 

ACTION     OF     POTASSIUM    THIOCYANATE 

UPON  SOME  IMIDE  CHLORIDES. 

[NINTH  PAPER.] 

BY  HENRY  Iy.  WHEELER  AND  H.  STANLEY  BRISTOL. 

No  attention  has  hitherto  been  given  to  the  action  of  potas- 
sium thiocyanate  upon  imide  chlorides.  It  was,  therefore,  im- 
possible to  predict  whether  normal  thiocyanates,  RSCN,  or 
isothiocyanates,  mustard  oils,  RNCS,  would  be  formed.  Most 
alkyl  halides  give  normal  thiocyanates,  while  the  acyl  hal- 


ides  give  isothiocyanates.     Imide  chlorides,    — C<^         ,    are 

x,0 

more  closely  related  to  acyl  halides,  — C^     ,  than  to  the  alkyl 

halides  and,  in  the  pyrimidine  series,  the  compounds  contain 
the  grouping  C— C — CC1,1  therefore  isothiocyanates  might  be 
expected  to  be  formed  in  this  reaction.  This  being  the  case, 
facilities  for  further  syntheses  would  be  increased. 

We  have  investigated  this  reaction  in  the  case  of  2-ethyl- 
mercapto-6-chlorpyrimidine,  2-ethylmercapto-5-brom-6-chlor- 
pyrimidine  and  2-ethylmercapto-5-methyl-6-chlorpyrimidine 
and  we  find,  in  each  instance,  that  the  chlorides  give  isothio- 
cyanates. 

The  preparation  of  derivatives  has  been  more  thoroughly 
carried  out  in  the  case  of  2-ethylmercapto-5-brom-6-chlor- 
pyrimidine,  III.,  than  with  the  other  chlorides.  This  was 
prepared,  as  already  shown,2  from  2-ethylmercapto-6-oxypyrim- 

1  Compare  Wheeler  and  Jamieson  :  J.  Am.  Chem.  Soc.,  24,  746  (1902). 

2  Wheeler  and  Johnson  :  THIS  JOURNAL,  31,  603  (1904). 


Researches  on  Pyrimidines.  449 

idine   (I.)    by  brominating    (!!.)»    then   chlorinating  in   the 
6-position. 

HN  -  CO  HN  -  CO  N—  —  CC1 

II  II  II 

C2H6SC         CH     —     C2H5SC         CBr    ~    C2H6SC          CBr 

II          II  II          II  II  II 

N  -  CH  N  -  CH  N  -  CH 

I.  II.  III. 

When  2-ethylmercapto-5-brom-6-chlorpyrimidine  was  boiled, 
in  toluene  solution,  with  potassium  thiocyanate,  2-ethylmer- 
capto-5-brom-6-isothiocyanpyrimidine  (IV.)  was  obtained. 
This  reacted  with  ammonia,  aniline,  etc.,  yielding  the  corre- 
sponding thiourea  derivatives. 

When,  however,  the  chlorbrommercaptopyrimidine  (III.) 
was  boiled  with  an  alcoholic  solution  of  potassium  thiocyanate, 
the  thionurethane  (V.)  was  obtained  and  this  compound,  with 
sodium  ethylate  and  ethyl  bromide,  gave  the  imidothiocar- 
bonic  ester  represented  by  Formula  VI. 

N—  =:CNCS  Nzi   =CNHCSOC2H6 

I 


C2H5SC  CBr  —       C2H6SC  CBr 


N CH 

V. 


N: 


C3H5SC          CBr 


VI. 

When  this  imidothiocarbonic  ester  derivative  was  treated 
with  alcoholic  ammonia,  it  evolved  mercaptan  and  the  pseudo- 
oxygen  urea  (VII.)  was  formed  smoothly.  This  gave  the  nor- 
mal urea  (VIII.)  when  treated  with  cold,  concentrated  hydro- 
chloric acid.  Boiling  hydrochloric  acid  then  gave  5-bromcy  to- 
sine  (X.).  Attempts  to  condense  the  pseudooxygen  urea,  or 
the  normal  urea,  to  a  purin  derivative  were  without  success. 
The  bromine  in  these  compounds  is  firmly  bound  but  the 
urea  and  pseudourea  groups  are  easily  removed. 


450  Wheeler  and  Bristol. 

When  the  pseudourea  (VII.)  was  heated  with  pyridine  or  aque- 
ous ammonia,  in  a  closed  tube,  2-ethylmercapto-5-brom-6-amino- 
pyrimidine  was  formed  (IX.).  The  same  result  was  obtained 
when  the  compound  was  boiled  with  formic  acid.  Sodium,  in 
boiling  benzene,  failed  to  remove  bromine  but  attacked  the 
pseudourea  grouping.  2-Ethylmercapto— 5-brom-6-amino- 
pyrimidine  was  also  obtained  when  the  normal  urea  was  heated 
above  its  melting-point. 

X)C2H5 
N=C—  N=C<  N ~C-NHCONH2 

I  I  XNH2  |  | 
C2H5SC          CBr                          —  C2H5SC           CBr 

II  II                                               II  II 
N CH                                          N CH 

VII.  VIII. 


— NH2 


C2H6SC          CBr  — 

II  II 

N CH 

IX. 

In  the  latter  part  of  this  article  some  new  uracil  and  cytosine 
derivatives  are  described. 

EXPERIMENTAL. 

2-Ethylmercapto-6-isothiocyanpyrimidine, 

N=C— NCS 

C2H5SC          CH         . — Fifteen  grams  of  2-ethylmercapto-6- 

'    II  II 

N CH 

chlorpyrimidine,1  boiling  at  135°  (24  mm.)  and  at  128°  (16 
mm.)  were  dissolved  in  20  cc.  of  toluene  and  25  grams  of  dry, 
powdered  potassium  thiocyanate  were  added.  The  mixture 
was  boiled,  in  a  paraffin-bath,  for  12  hours.  The  insoluble  salts 
were  then  removed  by  filtering,  the  toluene  was  evaporated 
and  the  residue  distilled  under  reduced  pressure.  It  boiled, 
for  the  most  part,  at  180°  (32  mm.).  The  distillate  solidified 

i  Wheeler  and  Johnson  :  THIS  JOURNAL,  29,  497  (1903)  ;  31,  596  (1904). 


Researches  on  Pyrimidines.  451 

and,  when  crystallized  from  benzene,  it  separated  in  small, 
light-yellow,  prismatic  plates  and  melted,  on  slowly  heating, 
at  175°. 

Calculated  for 

C7H7N3S2.  Found. 

N  21.32  21.53 

2-Ethylmercapto-6-thioureapyrimidine, 

N==C— NHCSNH2 


C2H5SC  CH  . — On  adding  concentrated  aqueous 

1    II  II 

N CH 

ammonia  to  a  portion  of  the  above  toluene  solution  containing 
the  isothiocyanate,  an  energetic  reaction  took  place,  with  evolu- 
tion of  heat  and  a  solid  mass  separated.  When  this  material 
was  crystallized  from  alcohol  it  formed  long,  thin,  colorless 
prisms  and  melted  at  214°.  It  was  difficultly  soluble  in  water. 

Calculated  for 
C7HioN4S2'  Found. 

N  26.17  25.83 

2-Ethylmercapto-6-phenylthioureapyrimidine  was  prepared  by 
adding  aniline  to  a  toluene  solution  of  the  pure  crystallized  iso- 
thiocyanate. A  solid  separated,  with  evolution  of  heat  and, 
when  crystallized  from  alcohol,  it  formed  a  felted  mass  of  long, 
colorless  needles  resembling  cotton.  It  was  almost  insoluble 
in  hot  water  and  fairly  soluble  in  hot  alcohol,  it  melted  at  205°. 

Calculated  foi 
CisHnN^Sa.  Found. 

N  19.31  19.10 

2-Ethylmercapto-6-thionethylurethanepyrimidine, 
-$=C— NHCS.  OC2H5 

C2H5vSC          CH.  .—When  5    grams  of  2-ethyl- 

II  II 

N CH 

mercapto-6-chlorpyrimidine  were  added  to  an  alcoholic  solu- 
tion of  2.8  grams  of  potassium  thiocyanate,  potassium  chloride 
separated  almost  at  once.  The  mixture  was  warmed  on  the 
water-bath  for  3  hours,  the  alcohol  was  then  evaporated  and 
the  residue  treated  with  water.  The  crude  product  weighed  6 


452  Wheeler  and  Bristol. 

grams  and,  when  crystallized  from  alcohol,  it  formed  long, 
thin,  light-}*ellow,  etched  plates,  melting  at  93°.  It  is  readily 
soluble  in  hot  alcohol  and  difficultly  soluble  in  cold. 

Calculated  for 
C9H13ON3S2.  Found. 

N  17.28  16.89 

When  this  urethane  was  boiled  with  concentrated  hydro- 
chloric acid,  until  mercaptan  ceased  being  evolved  and  then 
evaporated,  a  mixture  of  about  equal  quantities  of  uracil  and 
cytosine  was  obtained. 

2-Ethylmercapto-5-methyl-6-thioureapyrimidinc, 
N==C— NHCS— NH2 

C2H5SC          CCH3  .—Eleven  grams  of  2-ethylmer- 

II  II 

N CH 

capto-5-methyl-6-chlorpyrirnidine,  30  grams  of  dry,  finely  pow- 
dered potassium  thiocyanate  and  30  cc.  of  toluene  were  mixed 
and  boiled  for  7  hours,  in  an  oil-bath.  The  potassium  thio- 
cyanate was  added,  in  portions  of  10  grams,  from  time  to  time. 
The  mixture  was  filtered  and,  to  a  portion  of  the  solution, 
alcoholic  ammonia  was  added,  the  thioureapyrimidine  then 
separated  in  a  fairly  pure  state.  It  was  moderately  soluble  in 
hot  alcohol  and  benzene,  difficultly  soluble  in  cold  and  crys- 
tallized from  benzene  in  bunches  of  radiating  needles.  It  was 
difficultly  soluble  in  hot  water  and  melted,  to  a  clear  oil,  at 


Calculated  for 

Found. 


192°. 


N  24.56  24.30 

2-Ethylmercapto-5-methyl-6-thionurethanepyrimidine, 
N=C— NHCS.OC2H5 

C2H5SC          CCH3  .—Ten  grams  of   the  chloride 

II  II 

N CH 

were  boiled  with  15  grams  of  dry,  finely  powdered  potassium 
thiocyanate,  in  toluene,  for  15  hours.  Then  an  excess  of  alco- 
hol was  added  and  the  mixture  boiled  again  for  6  hours.  The 
solution  was  filtered  hot  and  evaporated  to  dryness,  the  residue 


Researches  on  Pyrimidines.  449 

idine    (I.)    by  brominating    (!!.)»    then   chlorinating   in   the 
6-position. 

HN CO  HN CO  N -CC1 

II  II  II 

C2H6SC         CH     —     C2H5SC         CBr    —    C2H6SC          CBr 

II          II                            II          II                           II  II 

N CH  N CH  N CH 

I.  II.  III. 

When  2-ethylmercapto-5-brom-6-chlorpyrimidine  was  boiled, 
in  toluene  solution,  with  potassium  thiocyanate,  2-ethylmer- 
capto-5-brom-6-isothiocyanpyrimidine  (IV.)  was  obtained. 
This  reacted  with  ammonia,  aniline,  etc. ,  yielding  the  corre- 
sponding thiourea  derivatives. 

When,  however,  the  chlorbrommercaptopyrimidine  (III.) 
was  boiled  with  an  alcoholic  solution  of  potassium  thiocyanate, 
the  thionurethane  (V.)  was  obtained  and  this  compound,  with 
sodium  ethylate  and  ethyl  bromide,  gave  the  imidothiocar- 
bonic  ester  represented  by  Formula  VI. 

N- CNCS  N CNHCSOC2H5 

C2H5SC  CBr  —       C2H6SC  CBr  ~ 

II  II  '    II  II 

N CH  N CH 

IV.  V. 

yOC2H5 

N=CN= C< 

I  I  XSC2H5 
C2H5SC          CBr 

II  II 
N CH 

VI. 

When  this  imidothiocarbonic  ester  derivative  was  treated 
with  alcoholic  ammonia,  it  evolved  mercaptan  and  the  pseudo- 
oxygen  urea  (VII.)  was  formed  smoothly.  This  gave  the  nor- 
mal urea  (VIII.)  when  treated  with  cold,  concentrated  hydro- 
chloric acid.  Boiling  hydrochloric  acid  then  gave  5-bromcyto- 
sine  (X.).  Attempts  to  condense  the  pseudooxygen  urea,  or 
the  normal  urea,  to  a  purin  derivative  were  without  success. 
The  bromine  in  these  compounds  is  firmly  bound  but  the 
urea  and  pseudourea  groups  are  easily  removed. 


450  Wheeler  and  Bristol. 

When  the  pseudourea  (VII. )  was  heated  with  pyridine  or  aque- 
ous ammonia,  in  a  closed  tube,  2-ethylmercapto-5-brom-6-amino- 
pyrimidine  was  formed  (IX.).  The  same  result  was  obtained 
when  the  compound  was  boiled  with  formic  acid.  Sodium,  in 
boiling  benzene,  failed  to  remove  bromine  but  attacked  the 
pseudourea  grouping.  2-Ethylmercapto-5-brom-6-amino- 
pyrimidine  was  also  obtained  when  the  normal  urea  was  heated 
above  its  melting-point. 

yOC2H5 

N=C—  N=C<  N ~C-NHCONH2 

I  I  XNH2  |  | 

C2H5SC  CBr  -~C,H6SC  CBr 

II  II 

N CH 

VIII. 


IX. 

In  the  latter  part  of  this  article  some  new  uracil  and  cytosine 
derivatives  are  described. 

EXPERIMENTAL. 

2-Ethylmercapto-6-isothiocyanpyrimidine, 

N=C— NCS 

C2H5SC  CH          .—Fifteen  grams   of  2-ethylmercapto-6- 

1    II  II 

N CH 

chlorpyrimidine,1  boiling  at  135°  (24  mm.)  and  at  128°  (16 
mm.)  were  dissolved  in  20  cc.  of  toluene  and  25  grams  of  dry, 
powdered  potassium  thiocyanate  were  added.  The  mixture 
was  boiled,  in  a  paraffin-bath,  for  12  hours.  The  insoluble  salts 
were  then  removed  by  filtering,  the  toluene  was  evaporated 
and  the  residue  distilled  under  reduced  pressure.  It  boiled, 
for  the  most  part,  at  180°  (32  mm.).  The  distillate  solidified 

i  Wheeler  and  Johnson  :  THIS  JOURNAL,  29,  497  (1903)  ;  31,  596  (1904). 


Researches  on  Pyrimidines.  451 

and,  when  crystallized  from  benzene,  it  separated  in  small, 
light-yellow,  prismatic  plates  and  melted,  on  slowly  heating, 
at  175°. 

Calculated  for 

CTH7N3S2.  Found. 

N  21.32  21.53 

2-Ethylmercapto-6-thioureapyrimidine, 
N=C— NHCSNH2 

C2H5SC          CH  . — On  adding  concentrated  aqueous 

'    II  II 

N CH 

ammonia  to  a  portion  of  the  above  toluene  solution  containing 
the  isothiocyanate,  an  energetic  reaction  took  place,  with  evolu- 
tion of  heat  and  a  solid  mass  separated.  When  this  material 
was  crystallized  from  alcohol  it  formed  long,  thin,  colorless 
prisms  and  melted  at  214°.  It  was  difficultly  soluble  in  water. 

Calculated  for 
C7H10N4S2-  Found. 

N  26.17  25.83 

2-Ethylmercapto-6-phenylthioureapyrimidine  was  prepared  by 
adding  aniline  to  a  toluene  solution  of  the  pure  crystallized  iso- 
thiocyanate. A  solid  separated,  with  evolution  of  heat  and, 
when  crystallized  from  alcohol,  it  formed  a  felted  mass  of  long, 
colorless  needles  resembling  cotton.  It  was  almost  insoluble 
in  hot  water  and  fairly  soluble  in  hot  alcohol,  it  melted  at  205°. 

Calculated  for 
Ci3H14N4S2.  Found. 

N  I9-31  19.10 

2-Ethylmercapto-6-thionethylurethanepyrimidine, 
N-   =C— NHCS.OC2H5 

I  I 

C2H5vSC          CH.  .—When  5    grams  of  2-ethyl- 

II  II 
N CH 

mercapto-6-chlorpyrimidine  were  added  to  an  alcoholic  solu- 
tion of  2.8  grams  of  potassium  thiocyanate,  potassium  chloride 
separated  almost  at  once.  The  mixture  was  warmed  on  the 
water-bath  for  3  hours,  the  alcohol  was  then  evaporated  and 
the  residue  treated  with  water.  The  crude  product  weighed  6 


452  Wheeler  and  Bristol. 

grams  and,  when  crystallized  from  alcohol,  it  formed  long, 
thin,  light-yellow,  etched  plates,  melting  at  93°.  It  is  readily 
soluble  in  hot  alcohol  and  difficultly  soluble  in  cold. 

Calculated  for 
CgH^ONsSg.  Found. 

N  17.28  16.89 

When  this  urethane  was  boiled  with  concentrated  hydro- 
chloric acid,  until  mercaptan  ceased  being  evolved  and  then 
evaporated,  a  mixture  of  about  equal  quantities  of  uracil  and 
cytosine  was  obtained. 

2-Ethylmercapto-5-methyl-6-thioureapyrimidine, 
N=C— NHCS— NH2 

I  I 

C2H5SC  CCH3  .—Eleven  grams  of  2-ethylmer- 

II  II 
N CH 

capto-5-methyl-6-chlorpyrimidine,  30  grams  of  dry,  finely  pow- 
dered potassium  thiocyanate  and  30  cc.  of  toluene  were  mixed 
and  boiled  for  7  hours,  in  an  oil-bath.  The  potassium  thio- 
cyanate was  added,  in  portions  of  10  grams,  from  time  to  time. 
The  mixture  was  filtered  and,  to  a  portion  of  the  solution, 
alcoholic  ammonia  was  added,  the  thioureapyrimidine  then 
separated  in  a  fairly  pure  state.  It  was  moderately  soluble  in 
hot  alcohol  and  benzene,  difficultly  soluble  in  cold  and  crys- 
tallized from  benzene  in  bunches  of  radiating  needles.  It  was 
difficultly  soluble  in  hot  water  and  melted,  to  a  clear  oil,  at 


192°, 


Calculated  for 
C8H12N4S2.  Found. 


N  24.56  24.30 

2-Ethylmercapto-5-methyl-6-thionurethanepyrimidine, 
N=C— NHCS.OC2H5 

C2H5SC          CCH3  .—Ten  grams  of   the  chloride 

II  II 

N CH 

were  boiled  with  15  grams  of  dry,  finely  powdered  potassium 
thiocyanate,  in  toluene,  for  15  hours.  Then  an  excess  of  alco- 
hol was  added  and  the  mixture  boiled  again  for  6  hours.  The 
solution  was  filtered  hot  and  evaporated  to  dryness,  the  residue 


Researches  on  Pyrimidines.  453 

treated  with  water  and  filtered.  It  was  then  taken  up  in 
alkali  and  extracted  with  ether,  the  alkaline  solution  acidified 
with  acetic  acid  and  the  pasty,  semi-solid  precipitate  filtered. 
This  was  dissolved  in  ether  and  dried  with  potassium  carbon- 
ate. On  evaporation  an  oil  was  obtained  which  solidified  com- 
pletely only  after  standing  9  months.  It  was  purified  by  dis- 
solving in  benzene  and  precipitating  with  ligroin,  whereupon 
groups  of  pale-yellow  prisms  separated.  It  melted  at  88°-89°, 
to  a  clear  oil.  It  was  readily  soluble  in  alcohol,  ether  and  ben- 
zene and  difficultly  soluble  in  water. 

Calculated  for 
C10H16ON3S2.  Found. 

N  16.34  16.71 

2-Ethylmercapto-5-brom-6-isothiocyanpyrimidine, 


C2H5SC          CBr     .  —  The     2-ethylmercapto-5-brom-6-chlor- 

II  II 

N  -  CH 

pyrimidine,  used  as  the  starting-point  for  the  following  experi- 
ments, was  described  in  a  previous  paper,1  but  the  boiling-point 
of  the  material  was  not  given.  It  was  observed  to  boil  at  168° 
(24-25  mm.)  and  at  i79°-i8o°  (36  mm.).  Fifteen  gram  por- 
tions of  the  chloride  were  dissolved  in  30  cc.  of  toluene  and  30 
grams  of  finely  pulverized,  dry  potassium  thiocyanate  were 
added,  in  portions  of  10  grams  each,  from  time  to  time.  The 
mixture  was  boiled  for  9  hours,  in  an  oil-bath.  It  was  then 
filtered  and  the  toluene  mostly  removed  by  evaporating  on  the 
water-bath,  under  diminished  pressure.  Petroleum  ether  was 
now  added,  in  slight  amount,  enough  to  separate  an  oily  sub- 
stance. The  solutions  were  quickly  poured  off  from  this 
through  a  filter  and,  on  standing,  beautiful,  small,  pale- 
yellow  prisms  formed,  which  were  purified  by  dissolving  in 
toluene  and  adding  a  small  amount  of  petroleum  ether.  The 
material  was  readily  soluble  in  benzene  and  toluene  and  diffi- 
cultly soluble  in  petroleum  ether.  It  melted  at  79°-8o°. 

Calculated  for 
CyHftNgSaBr.  Found. 

N  15.21  15.45 

1  Wheeler  and  Johnson:  THIS  JOURNAL,  31,  603  (1904). 


454  Wheeler  and  Bristol. 

2-Ethylmercapto-5-brom-6-thioureapyrimidine.  —  A  portion  of 
the  toluene  solution  of  the  isothiocyanate  was  mixed  with  alco- 
holic ammonia  in  excess.  Heat  was  evolved  and  the  thiourea 
separated  at  once.  It  was  found  to  be  difficultly  soluble  in 
water  and  alcohol  and  more  soluble  in  benzene,  from  which  it 
crystallized  in  light-yellow  plates,  melting  at  220°. 

Calculated  for 


Found. 

N  19.11  18.96 

2-Ethylmercapto-5-brom-6-phenylthioureapyrimidine.  —  Aniline 
acted  at  once,  with  evolution  of  heat,  on  the  isothiocyanate. 
The  product  was  difficultly  soluble  in  water,  fairly  soluble  in 
benzene,  it  separated  from  alcohol  in  the  form  of  a  felted  mass 
of  fine,  colorless  needles,  which  melted  at  i66°-i67°. 

Calculated  for 

Found. 


N  15.17  15.03 

2-Ethylmercapto-5-brom-6-thionethylurethanepyrimidine, 
N=^C—  NHCS.OC2H5 

C2H6SC  CBr  .—The    action    of   2-ethylmer- 


capto-5-brom-6-chlorpyrimidine  on  potassium  thiocyanate,  in 
alcoholic  solution,  was  not  smooth.  In  addition  to  the  thion- 
urethane,  two  other  compounds  were  isolated  as  products  of 
the  reaction.  These  were  2-ethylmercapto-5-brom-6-thio- 
pyrimidine  and  2-ethylmercapto-5-brom-6-aminopyrimidine. 

Thirty-three  grams  of  2-ethylmercapto-5-brom-6-chlorpyrimi- 
dine  were  added  to  a  concentrated  solution  of  20  grams  of  potas- 
sium thiocyanate  in  alcohol  and  the  mixture  was  boiled  for  several 
hours.  At  the  end  of  this  operation  the  odor  of  ethylthio- 
cyanate  was  noticed.  The  solution  was  filtered  and  the  alco- 
hol evaporated.  The  residue  was  treated  with  cold  benzene 
and  filtered,  leaving  2-ethylmercapto-5-brom-6-thiopyrimidine 
and  potassium  thiocyanate  undissolved.  The  benzene  was 
then  evaporated  and  the  residue  treated  with  dilute  sodium  hy- 
droxide and  extracted  with  ether.  The  ether  solution  con- 


Researches  on  Pyrimidines .  455 

tained  the  2-ethylmercapto-5-brom-6-aminopyrimidine,  melting 
at  124°,  which  was  described  in  a  previous  paper.1 

The  urethane  was  precipitated  from  the  alkaline  solution  by 
means  of  acetic  acid  ;  the  yield  of  crude  material  was  25  grams. 
It  was  readily  soluble  in  hot  alcohol,  difficultly  soluble  in  cold 
and  formed  long,  pointed,  light-yellow,  prismatic  plates,  melt- 
ing at  82°. 

In  two  other  experiments  18.5  grams  of  the  chloride  gave  13 
grams  of  the  urethane  and  15  grams  of  the  chloride  gave  11.5 
grams  of  the  urethane. 

Calculated  for 

C9H12ON8S2Br.  Found. 

N  13.04  12.97 

HN CS 

2-Ethylmercapto-5-brom-6-thiopyrimidine,     C«H5SC          CBr. 

II  II 

N CH 

— The  residue,  left  undissolved  by  cold  benzene,  in  the  above 
preparation  was  washed  with  water,  dried  and  crystallized 
from  benzene.  It  formed  pointed,  etched,  pale-yellow  plates 
and  melted,  with  slight  effervescence,  at  198°. 

Calculated  for 
C6H7N2S2Br.  Found. 

N  11.15  11.04 

In  the  course  of  some  other  work  Mr.  S.  H.  Clapp  prepared 
this  compound,  by  the  action  of  potassium  hydrosulphide  on 
2-ethylmercapto-5-brom-6-chlorpyrimidine.  When  this  prepa- 
ration was  mixed  with  the  above  the  melting-point  was  not 
altered. 

2-Ethylmercapto-^-brom-6-iminothioethylcarbonatepyrimidine, 

/SC2H6 
Nzz^rC— N=C< 

I  I  XOC2H5 

C2H,SC          CBr  . —Six  grams  of  the  above  thion- 

II  II 
N CH 

ethylurethane  were  dissolved  in  a  solution  of  0.42  gram  of 
sodium,  in  a  small  quantity  of  absolute  alcohol  and  then  4  grams 

1  THIS  JOURNAL,  31,  604  (1904). 


456  Wheeler  and  Bristol. 

of  ethyl  bromide  were  added.  On  standing  a  short  time  sodium 
bromide  separated.  The  mixture  was  warmed  on  the  steam- 
bath,  then  filtered  and  evaporated  to  dryness.  The  product  was 
treated  with  ether,  filtered  from  sodium  bromide  and  evapora- 
ted. The  residue,  on  cooling,  solidified.  The  yield  was  found 
to  be  6  grams.  The  product  was  purified  by  crystallizing 
from  alcohol  containing  a  little  water.  It  then  formed  long, 
colorless  prisms,  melting  at  43°,  which  were  readily  soluble  in 
alcohol,  ether  and  warm  ligroin  but  insoluble  in  water. 

Calculated  for 

CnH16ON8S2Br.  Found. 

N  12. oo  11.87 

2-Ethylmercapto-5-brom-6-pseudoethylureapyrimidine, 
N=C— N=C— OC2H5 

C2H5SC          CBr       NH2  .—This  was  formed,  quantita- 

II  II 

N CH 

tively,  by  passing  ammonia  gas  into  an  alcoholic  solution  of 
the  above  aminothioethylcarbonate.  It  crystallized  from  alco- 
hol in  beautiful,  long  needles,  which  developed  into  thin  plates, 
melting  at  1 10°  and  decomposing  about  230°,  forming  a  tarry 
mass  on  cooling.  It  was  difficultly  soluble  in  hot  water  and 
insoluble  in  cold,  dissolved  readily  in  cold  benzene  and  warm 
alcohol.  It  was  insoluble  in  alkali  and  soluble  in  hydrochloric 
acid. 

Calculated  for 

C9H13ON4SBr.  Found. 

N  18.3  18.1 

This  material  can  be  boiled  with  pyridine  (3  hours)  or 
dimethyl  aniline  (10  minutes)  and  recovered  unaltered.  No 
bromine  is  removed  under  these  conditions.  When  heated 
with  pyridine  at  i8o°-i9O°,  in  a  closed  tube,  for  5  hours,  the 
only  crystalline  substance  obtained  was  2-ethylmercapto-5- 
brom-6-aniinopyrimidine.  This  substance  was  also  obtained 
when  the  material  was  boiled  with  formic  acid.  A  nitrogen 
determination  gave  17.7  per  cent,  while  the  calculated  is  17.9 
per  cent.  The  action  of  concentrated  aqueous  ammonia,  in  a 
closed  tube,  first  at  90°  for  3  hours,  then  at  145°- 150°  for  4$ 


Researches  on  Pyrimidines.  457 

hours,  gave  the  same  result.  The  hydrochloride  of  this  base 
was  obtained  when  the  pseudourea  was  warmed,  for  a  short 
time,  with  concentrated  hydrochloric  acid.  About  0.5  gram 
of  the  pseudourea  was  dissolved  in  benzene  and  treated  with 
an  excess  of  sodium,  the  mixture  was  boiled  for  12  hours. 
The  metal  became  coated  with  a  thick  deposit  and,  on  filtering 
and  evaporating  the  benzene,  there  was  no  residue.  The 
sodium  and  coating  was  treated  with  alcohol  and  a  portion  was 
acidified  with  nitric  acid,  whereupon  silver  nitrate  gave  no  in- 
soluble precipitate,  and,  therefore,  no  bromine  had  been  re- 
moved. On  acidifying  the  alkaline  solution  with  acetic  acid 
and  evaporating,  a  substance  was  obtained  melting  at  287°, 
with  effervescence.  On  dissolving  in  acetone  and  precipitating 
with  ether  it  effervesced  at  310°.  It  was  concluded  that  this 
material  was  2-ethylmercapto-5-brom-6-cyanamidepyrimidine,  not 
only  from  its  mode  of  formation,  but  also  because,  on  warm- 
ing with  dilute  hydrochloric  acid,  it  gave  the  following  urea 
derivative  : 

2-Ethylmercapto-5-brom-6-ureapyrimidme, 

N=C— NHCONH, 

I  | 

C2H5SC          CBr  . — This  was  also  produced  by  al- 

'    II  II 

N CH 

lowing  the  above  pseudourea  to  stand  dissolved  in  cold  con- 
centrated hydrochloric  acid.  After  several  days  the  urea 
separated  on  adding  water.  It  crystallized  from  alcohol  in 
short,  pointed  plates  which,  on  long  standing,  developed  into 
stout  prisms  and  melted,  when  slowly  heated,  at  167°. 

Calculated  for 

C7H9ON4SBr.  Found. 

N  2O.2  19.8 

If  this  material  is  heated  to  its  melting-point,  cooled  and  re- 
heated, it  melts  unaltered.  If  the  heating  is  continued  a  little 
above  its  melting-point  it  slowly  becomes  semi -solid.  One 
gram  of  the  urea  derivative  was  heated,  in  a  test-tube,  at  170°- 
180°,  a  portion  sublimed,  crystallizing  in  prismatic  plates  in 
the  cool  part  of  the  tube.  This  melted  at  124°  and,  when 


458  Wheeler  "and  Bristol. 

mixed  with  some  2-ethylmercapto-5-brom-6-aminopyrimidine, 
the  melting-point  was  not  altered. 

When  this  urea  was  boiled  with  concentrated  hydrochloric 
acid  5-bromcytosine1  was  obtained. 

HN CO 

I  | 

2-Thiouracil,   SC          CH. — This  compound  was  first   ob- 

I  II 

HN CH 

tained ,  along  with  2-ethylmercapto-6-oxypyrimidine,  when  pseu- 
doethylthiourea,  containing  some  thiourea,  was  condensed  with 
ethyl  sodium  formylacetate.  A  concentrated  aqueous  solution 
of  150  grams  of  ethyl  sodium  formylacetate  was  mixed  with  a 
saturated  solution  of  50  grams  of  thiourea.  The  mixture  was 
then  warmed  on  the  steam-bath  for  a  short  time,  cooled  and 
the  deep  red  solution  was  precipitated  with  a  slight  excess  of 
acetic  acid.  A  yellowish- white,  granular  precipitate  separated, 
weighing  50  grams.  This  crystallized  from  alcohol  or  water 
in  colorless  prisms.  It  is  difficultly  soluble  in  these  solvents. 
When  heated,  it  effervesces  above  300°. 

Calculated  for 
C4H4ON2S.  Found. 

N  21.8  21.9 

2-Ethylmercaplo-6-anilinopyrimidine  hydrochloride  was  pre- 
pared by  mixing  2-ethylmercapto-6-chlorpyrimidine  (10  grams) 
with  aniline  (5.3  grams),  after  standing  over  night,  then  warm- 
ing on  the  water-bath  for  several  hours,  the  mixture  solidified. 
It  was  readily  soluble  in  hot  alcohol  and  hot  water  and  crys- 
tallized in  the  form  of  colorless  needles  or  prisms.  It  melted 
at  198°  with  effervescence. 

Calculated  for 
C12HMN8SC1.  Found. 

N  15-7  15-9 

When  this  hydrochloride  was  dissolved  in  hot  water  and  pre- 
cipitated with  ammonia,  an  oil  separated.  This  finally  solidi- 
fied and  was  purified  by  repeatedly  dissolving  in  alcohol  and 
precipitating  with  water.  The  base  is  very  soluble  in  alcohol. 
It  formed  fine,  colorless  needles  and  melted  at  68°. 

1  THIS  JOURNAL,  31,  604  (1904). 


Researches  on  Pyrimidines.  459 

Calculated  for 
Ci2Hi3N3S.  Found. 

N  18.1  18.2 

2-Oxy-6-anilinopyrimidine  (  Phenylcytosine)  , 


—  NHC6H6 


OC          CH  .—The  hydrochloride  of  this  base  was 


HN- 


-CH 


obtained  by  boiling  the  above  hydrochloride  with  strong  hydro- 
chloric acid.  It  formed  colorless  needles  or  prisms,  from  water 
or  alcohol,  which  effervesced  at  228°.  This  material  was  dis- 
solved in  hot  water  and  ammonia  was  added,  whereupon 
bunches  of  colorless  needles  separated.  Unlike  cytosine,  this 
substance  crystallizes  without  water  of  crystallization.  It  is 
fairly  soluble  in  hot  alcohol  and,  from  this  solvent,  it  sepa- 
rates in  beautiful,  colorless,  six-sided  plates.  When  slowly 
heated  it  melted  at  about  269°. 

Calculated  for 
CioHioON3.  Found. 

N  22.3  22.6 

The  chlorplatinate  formed  groups  of  radiating  yellow  prisms. 
A  platinum  and  water  determination  agreed  with  the  calcula- 
ted for  a  normal  salt  with  i  molecule  of  water  of  crystalliza- 
tion. The  formation  of  platinum  chloride  double  salts  with 
water  of  crystallization  seems  to  be  of  frequent  occurrence  in 
the  pyrimidine  series. 

Calculated  for 

Found. 


Pt  24.24  24.31 

H2O  0.22  0.26 

N:  -  C—  NHC,H6 
2,6-Dianilinopyrimidine,  C6H5NHC          CH  .—The 

N  -  CH 

hydrochloride  of  this  base  was  obtained  when  2-ethylmercapto- 
6-chlorpyrimidine  was  heated  to  150°,  with  2  molecular  propor- 
tions of  aniline.  The  compound  formed  arborescent  needles 
from  alcohol  and  melted  at  197°. 

Calculated  for 
CuHi5N4Cl.  Found. 

N  18.76  18.59 


460  Wheeler  and  Bristol. 

The  free  base,  obtained  by  boiling  the  hydrochloride  with 
aqueous  ammonia,  crystallized  from  alcohol  in  six-sided  plates. 
It  is  insoluble  in  water  and  fairly  soluble  in  hot  benzene  and 
ether.  It  melted  at  136°-: 37°. 

Calculated  for 

CieH14N4.  Found. 

N  21.38  21.42 

HN CO 

I       I 

2-Ethylmercapto-5-phenyluracil,  C2H5SC  CC6H5,  was  ob- 

II  II 

N CH 

tained  by  condensing  sodium  phenylformylethylacetate1  with 
the  ethyl  iodide  addition-product  of  thiourea,  in  alkaline  solu- 
tion. The  yield  was  very  poor.  The  substance  crystallized 
from  alcohol  in  long,  needle-like  prisms,  melting  at  158°.  In 
alcohol  and  hot  water  it  is  readily  soluble. 

Calculated  for 
Ci2HJ2ON2S.  Found. 

N  12. 07  12.12 


HN- 

I 

5-Phenyluracil,   OC  CC6H5. — When  the  above  compound 

HN -CH 

was  digested  on  the  steam-bath,  with  concentrated  hydrochloric 
acid,  for  a  number  of  hours,  mercaptan  was  evolved  and  diffi- 
cultly soluble  material  was  obtained.  The  product  was  spar- 
ingly soluble  in  hot  alcohol  and  water,  but  it  separated  from 
these  solutions,  on  cooling,  in  a  flocculent  mass  of  what  ap- 
peared to  be  microscopic  plates.  It  did  not  melt  at  350°.  It 
is  soluble  in  alkali  and  can  be  precipitated  unaltered  by  hydro- 
chloric acid. 

Calculated  for 
CioH8O2N2.  Found. 

N  14.89  14.87 

The  isomeric  4-phenyluracil  has  been  described  by  Fischer 
and  Roeder2  and  it  was  also  obtained  by  one  of  us.3 

NEW  HAVEN,  CONN., 
January,  1905. 

1  Wislicenus  :  Ber.  d.  chem.  Ges.,  20,  2933  (1887). 

2  Ibid.,  34,  3751  (1901). 

8  Wheeler  and  Merriam  :  THIS  JOURNAL,  39,  490  (1903). 


[Reprinted  from  the  American  Chemical  Journal,    Vol.  XXXIV,     No.  3. 
September,  1905.] 


Contributions  from  the  Sheffield  Laboratory  of  Yale  University. 

CXXV.— RESEARCHES  ON  PYRIMIDINES  :  THE  AC- 
TION OF  AQUEOUS  AND  ALCOHOLIC  AMMO- 
NIA AND  ANILINE  ON  SOME  HALO- 
GEN   AND    MERCAPTO    PYR- 
IMIDINES. 

[TENTH  PAPER.] 

BY  TREAT  B.  JOHNSON  AND  CARL  O.  JOHNS. 

The  object  of  this  paper  is  to  describe  the  behavior  of  cer- 
tain halogen  and  mercapto  pyrimidines  towards  ammoniacal 
solutions  and  aniline. 

We  have  had  occasion,  in  the  preparation  of  aminopyrimi- 
dines,  to  use  both  aqueous  and  alcoholic  solutions  of  ammonia 
to  replace,  with  the  amino  group,  halogens  and  mercapto  radicals 
in  pyrimidines.  We  have  been  greatly  impressed,  in  the 
course  of  this  work,  with  the  remarkable  difference  in  degree 
of  reactivity  of  aqueous  and  alcoholic  ammonia  towards  such 
pyrimidine  derivatives. 

In  a  recent  publication  from  this  laboratory,  by  Wheeler  and 


176  Johnson  and  Johns. 

Jamieson,1  it  was  shown  that  when  2-methylmercapto-5-methyl- 
4,6-dichlorpyrimidine  was  heated  with  alcoholic  methylamine, 
only  i  chlorine  atom  was  removed  and  2-methylmercapto-4- 
chlor-5-methyl-6-methylamino  pyrimidine  was  the  product  of  the 
reaction.  An  analogous  result  was  obtained  when  2-methylmer- 
capto-4,6-dichlorpyrimidine  was  heated  with  alcoholic  ammo- 
nia. It  was  converted,  practically  quantitatively,  into 
2-methylmercapto-4-chlor-6-aminopyrimidine.  They  did  not 
succeed  in  converting  this  chloraminopyrimidine  into  the  cor- 
responding diaminopyrimidine  (I.)  by  heating  with  alcoholic 
ammonia.  We  now  find  that  the  2-methylmercapto-4-chlor-6- 
aminopyrimidine  is  converted,  quantitatively,  into  2-methyl- 
mercapto-4,6-diaminopyrimidine  (I.)  when  heated  with 
aqueous  ammonia,  at  i85°-i95°  : 
N=  =zCNH2 

I  I 

CH3SC  CH       -j-  aqueous  ammonia     = 

II  II 

N  -  CC1 


CH3SC  CH       -f  NH4C1. 

II  II 

N  -  CNH2 

I. 

It  seemed  of  interest,  in  connection  with  this  result,  to  com- 
pare the  behavior  of  aqueous  and  alcoholic  ammonia  towards 
2-methylmercapto-4-chlor-5-brom-6-aminopyrimidine.  This 
compound  reacts  in  an  analogous  manner  to  the  above  2-methyl- 
mercapto-4-chlor-6-aminopyrimidine.  It  can  be  recovered  un- 
altered after  heating  with  concentrated  alcoholic  ammonia,  at 
i5O°-i6o°.  When  heated  with  aqueous  ammonia,  under  the 
same  conditions,  (i5o°-i6o°),  it  was  converted,  quantitatively, 
into  2-methylinercapto-5-brom-4,  6-diaminopyrimidine, 
N=  =CNH2 

I  I 

CH3SC  CBr      +  aqueous  ammonia     = 

II  II 
N  -  CC1 

i  THIS  JOURNAL,  33,  343  (1904). 


Researches  on  Pyrimidines.  177 

N=   =CNH2 

I  I 

CH3SC          CBr      +  NH4C1. 


II. 


It  would  appear,  from  the  results  of  these  two  experiments, 
that  a  halogen  is  more  easily  replaced  by  the  amino  group 
when  aqueous  ammonia  is  used.  In  order  to  test  this  assump- 
tion further  and  to  compare  the  action  of  ammoniacal  solutions 
in  another  series,  we  have  examined  the  comparative  behavior 
of  2-ethylmercapto-6-chlorpyrimidine  (III.)  and  2-ethylmer- 
capto-5-brom-6-chlorpyrimidine1  (IV.)  towards  aqueous  and 
alcoholic  ammonia  : 

N=  =CC1  N—  —  CC1 

II  II 

C2H5SC          CH,  C2H5SC          CBr. 

II  II  II  II 

N  --  CH  N  -  CH 

III.  IV. 

Wheeler  and  Johnson2  observed  that  2-ethylmercapto-6- 
chlorpyrimidine  reacts  with  alcoholic  ammonia,  at  140°—  1  50°, 
to  form  2-ethylmercapto-6-aminopyrimidine3  (V.).  We  now 
find  that  this  same  chlorpyrimidine  can  be  heated  with  aqueous 
ammonia,  at  the  same  temperature,  (i4O°-i5o°)  and  be  re- 
covered unaltered.  A  most  remarkable  case  of  lack  of  analogy 
was  observed  when  we  examined  the  behavior  of  ammoniacal 
solutions  towards  2-ethylmercapto-5-brom-6-chlorpyritnidine 
(IV.).  This  pyrimidine  was  converted,  quantitatively,  into 
2-ethylmercapto-5-brom-6-aminopyrimidine  (VI.)  when  heated 
with  alcoholic  ammonia,  at  i2O°-i3O°  and  also  when  heated 
with  aqueous  ammonia,  at  i4O°-i5O°. 

1  Wheeler  and  Johnson  :  THIS  JOURNAL,  31,  603  (1904). 
.  2  Ibid.,  29,  492  (1903). 

3  It  has  been  our  experience,  since  the  publication  of  this  paper,  that  the  best 
yield  of  this  2-ethylmercapto-6-aminopyrimidine  is  obtained  when  the  chloride  is 
heated  with  alcoholic  ammonia,  at  I2o°-i3o°,  for  3  or  4  hours.  x.  B.  j. 


178  Johnson  and  Johns. 

N  --  CCI 

I  I 

C2H5SC  CH  +  alcoholic  ammonia     = 

l|  ||  (I20°-I300) 

N  -  CH 

N=CNH2 

C 


C2H5SC  CH      +  NH4C1. 

II  II 

N  -  CH 

V. 


N=   =CC1 


C2H5SC  CBr  +  aqueous  or  alcoholic  ammonia     = 

||  ||  (i4o°-i5o°) 

N  -  CH 

N  -  CNH, 

CaH5SC  CBr       4-  NH4C1. 

II  II 

N  -  CH 
VI. 

The  abnormal  behavior  of  ammoniacal  solutions  was  also  il- 
lustrated when  we  tried  to  replace  the  mercapto  radical,  in  cer- 
tain pyrimidines,  with  the  amino  group.  2-Methylmercapto- 
4,6-diaminopyrimidine1  (VII.)  and  2-methylmercapto-5-brom- 
4,  6-diaminopyrimidine  (VIII.)  were  recovered  unaltered,  after 
heating  with  both  aqueous  and  alcoholic  ammonia,  at  205°- 
215°.  These  two  negative  results  were  of  especial  interest 


1M 

V  .  I\  H  2 

1\ 

^  -iM  Ha 

I 

CH3SC 

II 

TSJ 

I 

CH     , 

II 

fWHT 

CH,SC 

II 

TM 

CBr 

II 

PATTT 

VII.  VIII. 

when  compared  with  the  behavior  of  2-ethylmercapto-6-chlor- 
pyrimidine2  and  2-ethylmercapto-5-brom-6-chlorpyrimidine3 
towards  aqueous  ammonia,  at  high  temperatures.  When 

1  Wheeler  and  Jamieson  :  Loc,  cit. 

2  Wheeler  and  Johnson  :  THIS  JOURNAL,  39,  496  (1903). 
8  Wheeler  and  Johnson  :  Ibid.,  31,  603  (1904). 


Researches  on  Pyrimidines.  179 

2-ethylmercapto-6-chlorpyrimidine  was  heated  with  aqueous 
ammonia,  at  i85°-i95°,  2,6-diaminopyrimidine1  (IX)  was  the 
product  of  the  reaction.  On  the  other  hand,  when  2-ethylmer- 
capto-5-brom-6-chlorpyrimidine  was  heated,  under  practically 
the  same  conditions,  (i9O°-2OO°)  with  aqueous  ammonia,  the 
chlorine  atom  only  was  removed  and  2-ethylmercapto-5-brom- 
6-amiuopyrimidine  (X.)  was  formed  : 

N=  — CC1 

I  I 

C2H5SC  CH  -f-  aqueous  ammonia     = 

||  ||  (i85°-i95°) 

N CH 

N CNH2 

I  I 

NH2C  CH      -f-  NH4C1  +  C2H5SH. 

II  II 
N CH 

IX. 

N=   ziCCl 

I  I 

C2H5SC  CBr  -f-  aqueous  ammonia     = 

||  ||  (I90°-200°) 

N CH 

N CNH2 

C2H6SC  CBr      +  NH4C1. 

II  II 

N CH 

X. 

It  has  been  our  experience  that  a  mercapto  group  is  more 
easily  replaced  by  the  anilido — NHC6H5 — than  by  the  amino 
group.  When  2-methylmercapto-4-chlor-6-aminopyrimidine 
was  heated  with  i  molecular  proportion  of  aniline,  at  120°- 
130°,  2-methylmercapto-4-anilido-6-aminopyrimidine  (XI.) 
was  formed.  On  the  other  hand,  when  heated  with  2  molec- 
ular proportions  of  aniline,  at  140°-! 50°,  2,4-dianilido-6- 
aminopyrimidine  (XII.)  was  the  product  of  the  reaction. 

1  Biittner :  Ber.  d.  chem.  Ges.,  36,  2233. 


180  Johnson  and  Johns. 

N CNH2 

CH3SC  CH      +  C6H5NH2     == 

II  II 

N CC1 


N :CNH2 

CH3SC  CH  +  HC1. 

II  II 

N CNHC6H6 

XI. 


JN 

UJNri 

1 

1 

CHSSC 

II 

CH 

II 

+  2C6H6NH2 

= 

II 

N 

II 
CC1 

N' 

/^\"KTTT 

CNH2 

i 

I 

CtH6NHC 

CH 

N 


CH       +  HC1  -f  C2H5SH. 

II 
CNHC6H6 


XII. 


These  results  are  analogous  to  that  obtained  by  Wheeler 
and  Bristol.1  They  observed  that  2-ethylmercapto-6-chlor- 
pyrimidine  reacted  with  i  molecular  proportion  of  aniline,  at 
100°,  to  form  2-ethylmercapto-6-anilidopyrimidine  (XIII.). 
When  the  same  mercaptochlorpyrimidine  was  heated  with  2 
molecular  proportions  of  aniline,  at  150°,  it  was  converted  into 
2,6-dianilidopyrimidine  (XIV.)  : 


Nn=CNHC6H5 

C2H6SC          CH 

II  II 

N  -  CH 
XIII. 


N 

C6H5NHC 

II 
N 


CNHC6H5 

CH 

II 
CH 


XIV. 


2-Methylmercapto-4-anilido-6-aminopyrimidine  (XI.)  reacts 
with  bromine,  in  glacial  acetic  acid,  to  form  a  dibrom  substitu- 

i  THIS  JOURNAL,  33,  448  (1905). 


Researches  on  Pyrimidines.  181 

tion-product,  melting  at  202°.  In  order  to  establish  the  struc- 
ture of  this  body  it  was  necessary  to  decide  whether  i  or  2 
bromine  atoms  had  entered  the  benzene  nucleus  ;  whether 
2-methylmercapto-4-dibromanilido-6-aminopyrimidine  (XV. ) 
or  2-methylmercapto-4-parabromanilido-5-brom-6-aminopyrim- 
idine  (XVI.)  was  the  product  of  the  reaction.  The  following 
experiment  proved  that  formula  XVI.  represents  the  structure 


N=   =CNH 


CH3SC 

II  I  /Br 

N CNH.C6H3< 

XBr 

^LV.  ~KVI. 

of  this  dibrompyrimidine.  The  same  derivative,  melting  at 
202°,  was  obtained  when  2-methylmercapto-4-chlor-5-brom-6- 
aminopyrimidine  was  heated  with  parabromaniline  : 


C8H 

\Br(4) 

N=  =CNH, 

I  I 

CH8SC          CBr  +  HC1. 

II  II 

N CNHC.H4Br 

EXPERIMENTAL. 

2-Methylmerca,pto-4.-oxy-6-aminopyrimidine, 
N — — CNH, 

I  I 

CH,SC  CH2   . — This  mercaptopyrimidine  was  easily  pre- 

N CO 

pared    by  dissolving  2-thio-4-oxy-6-aminopyrimidine1  in  alco- 

1  The  2-thio-4-oxy-6-aminopyrimidine  used  for  this  preparation  was  made  accord- 
ing to  Traube's  directions,  by  condensing  thiourea  with  cyanethylacetate,  in  presence 
of  sodium  ethylate.  Ann.  Chem.  (I^iebig),  331,  71. 


1 82  Johnson  and  Johns. 

hoi,  containing  i  molecular  proportion  of  sodium  ethylate  and 
then  warming  on  the  steam-bath  with  i  molecular  proportion 
of  methyl  iodide.  The  reaction  is  exceedingly  smooth  and  in 
a  few  minutes  the  mercapto  derivative  separates  from  the  alco- 
holic solution.  The  pyrimidine  was  purified  by  evaporating 
the  excess  of  alcohol  and  then  washing  the  crystalline  residue 
with  cold  water,  to  remove  sodium  iodide.  It  was  difficultly 
soluble  in  hot  alcohol,  from  which  it  separated  in  colorless 
plates.  It  decomposed  at  267°  with  effervescence.  The  yield 
was  practically  quantitative.  Analysis  : 

Calculated  for 
C5HrON3S.  Found. 

N  26.75  26.97 

2-Methylmercapto-4.-methoxy-6-aminopyrimidine, 
N=   =C.NH2 

I  I 

CHSSC  CH       .  —  This  compound   was  obtained   when 

II  II 

N COCH3 

2-thio-4-oxy-6-aminopyrimidine  was  warmed,  in  alcohol,  with  2 
molecular  proportions  of  sodium  ethylate  and  methyl  iodide. 
It  was  soluble  in  acids  but  insoluble  in  alkali.  It  was  purified 
by  crystallizing  from  alcohol,  from  which  it  separated,  on  cool- 
ing, in  long,  well-developed  prisms.  It  melted  at  256°,  with- 
out effervescence,  to  a  clear  oil.  Analysis  (Kjeldahl)  : 

Calculated  for 
C6H9ON3S.  Found. 

N  24.55  24.46 

2-Methylmercapto-^.-oxy-^-brom-6-aminopyrimidine, 

N=   =CNH2 

I  I 

CH3SC  CHBr,  was  prepared  by  dissolving  2-methylmer- 

II  I 
N CO 

capto-4-oxy-6-aminopyrimidine  in  glacial  acetic  acid  and  then 
adding  the  calculated  quantity  of  bromine.  The  bromine  color 
disappeared  at  once  and  the  pyrimidine  separated  as  a  beauti- 
ful, crystalline  powder.  It  was  difficultly  soluble  in  water  and 


Researches  on  Pyrimidines.  183 

alcohol.  It  crystallized  from  hot  acetic  acid  in  slender  prisms. 
It  had  no  definite  melting-point,  but  began  to  turn  brown  at 
200°  and  did  not  melt  below  300°.  Analysis  (Kjeldahl)  : 

Calculated  for 
C5H6ON3SBr.  Found. 

N  17.79  17.76 

2-Ethylmercapto-4.-oxy-6-aminopyrimidine, 
N=CNH2 

I  I 

C2H5SC          CH2    . — This  compound  was  prepared  in  a  man- 

'    II  i 

N CO 

ner  similar  to  that  used  for  the  preparation  of  2-methylmer- 
capto-4-oxy-6-aminopyrimidine,  by  warming  2-thio-4-oxy-6- 
aminopyrimidine,  in  alcohol,  with  molecular  proportions  of 
sodium  ethylate  and  ethyl  bromide.  It  was  very  soluble  in 
alcohol.  It  crystallized  from  water  in  long,  slender  prisms 
and  melted  at  2i6°-2i7°,  to  a  clear  oil.  Analysis  (Kjeldahl)  : 

Calculated  for 
C6H9ON3S.  Found. 

N  24.56  24.37 

2-Methylmercapto-4-chlor-6-aminopyrim2dine, 
N :CNH2 

I  I 

CH3SC  CH     . — This  derivative  was  previously  described 

II  II 
N CC1 

by  Wheeler  and  Jamieson,1  who  obtained  it  by  heating 
2-methylmercapto-4,6-dichlorpyrimidine  with  alcoholic  ammo- 
nia. We  find  that  it  can  be  prepared  more  easily  by  treating 
2-methylmercapto-4-oxy-6-aminopyrimidine  with  phosphorus 
oxy chloride.  The  pyrimidine  was  boiled  with  an  excess  of 
phosphorus  oxychloride  until  the  evolution  of  hydrochloric 
acid  ceased.  The  clear  solution  which  resulted  was  then 
heated  to  100°,  under  diminished  pressure,  to  remove  the  ex- 
cess of  phosphorus  oxychloride.  A  brittle,  amorphous  residue 
was  obtained.  This  proved  to  be  a  mixture  of  the  hydrochlo- 
ride  of  the  unaltered  pyrimidine  and  an  unstable  phosphorus  de- 

i  THIS  JOURNAL,  33,  343  (1904). 


184  Johnson  and  Johns. 

rivative  of  the  mercaptochlorpyrimidine.  The  amorphous 
residue  was  carefully  decomposed  with  ice-water.  We  ob- 
tained a  clear,  yellow  solution,  which  was  then  made  distinctly 
alkaline  with  ammonium  hydroxide  and  concentrated  by 
evaporation  on  the  steam-bath.  Upon  cooling,  a  crystalline 
product  separated  which  proved  to  be  a  mixture  of  the 
2-methylmercapto-4-chlor-6-aminopyrimidine  and  unaltered 
2-methylmercapto-4-oxy-6-aminopyrimidine.  A  separation  of 
the  two  compounds  was  effected  by  washing  with  dilute  sodium 
hydroxide  solution,  in  which  the  chlorpyrimidine  is  insoluble. 
It  was  further  purified  by  recrystallizing  from  water.  It 
agreed  in  all  its  properties  with  the  compound  described  by 
Wheeler  and  Jamieson,1  except  that  we  found  it  to  melt  at  132° 
instead  of  i26°-i27°.  Analysis  (Kjeldahl)  : 

Calculated  for 
C6H6N3SC1.  Found. 

N  23.93  23.86 

In  our  experiments  in  the  preparation  of  the  above  2-methyl- 
mercapto-4-chlor-6-aminopyrimidine  we  have  usually  obtained 
only  about  45-50  per  cent  of  the  theoretical  yield.  In  one  ex- 
periment the  yield  corresponded  to  59.  6  per  cent  of  the  theoretical. 
In  nearly  every  case  we  recovered,  unaltered,  about  one-half 
of  the  2-methylmercapto-4-oxy-6-aminopyrimidine.  Phos- 
phorus pentachloride  was  used  in  one  experiment  in  place  of 
phosphorus  oxychloride,  but  the  reaction  was  not  as  smooth 
and  more  decomposition-products  were  formed. 

2-Methylmercapto-4,6-diaminopyrimidine, 
N  -  .CNH2 

I  | 

CH3SC          CH      .  —  This  compound  has  been  described  in  a 

II  II 

N  -  CNH2 

previous  paper  from  this  laboratory.2  We  prepared  it  by 
heating  the  above  2-methylmercapto-4-chlor-6-aminopyrimi- 
dine  with  concentrated  aqueous  ammonia,  at  i85°-i95°,  for  5 
hours.  When  the  tube  was  opened  we  obtained  a  colorless 
solution  which  was  immediately  concentrated  on  the  steam- 


cit. 
2  Wheeler  and  Jamieson  :  Loc.  cit. 


Researches  on  Pyrimidines.  185 

bath.  Upon  cooling,  a  beautiful,  crystalline  body  separated, 
which  was  purified  by  recrystallizing  from  water  and  alcohol. 
It  deposited  in  lenticular-shaped  crystals  and  melted  at  184°- 
185°,  to  a  clear  oil.  Analysis  (Kjeldahl)  : 

Calculated  for 

C5H8N4S.  Found. 

N  35-89  35-54 

This  mercaptodiaminopyrimidine  is  very  stable  in  the  pres- 
ence of  aqueous  and  alcoholic  ammonia  solutions.  It  was  re- 
covered, unaltered,  after  heating  with  concentrated  aqueous 
ammonia,  for  7  hours,  at  2O5°-2i5°.  It  was  then  heated  with 
a  saturated,  alcoholic  solution  of  ammonia,  for  7  hours,  at 
2O5°-2i5°.  The  pyrimidine  was  again  recovered  unaltered 
and  melted  sharply  at  184°-! 85°. 

2-Methylmercapto-4-chlor-5-brom-6-amino  pyrimidine, 
N. CNH2 

CH3SC  CBr    ,   was  obtained  in  the  form  of  its  hydro- 

II  li 

N CC1 

bromic  acid  salt,  when  a  molecular  proportion  of  bromine  was 
added  to  an  acetic  acid  solution  of  2-methylmercapto-4-chlor- 
6-aminopyrimidine.  The  hydrobromide  sintered  at  about 
i8o°-i9o°  and  then  decomposed  at  208°,  with  violent  efferves- 
cence. It  was  purified  for  analysis  by  crystallizing  from  acetic 
acid,  from  which  it  separated,  on  cooling,  in  stout  prisms. 
Analysis : 

Calculated  for 

C5H6N8SClBr2.  Found. 

N  12.51  12.56 

The  pyrimidine  base  was  easily  obtained  from  its  salt  by 
treating  with  a  10  per  cent  solution  of  sodium  hydroxide.  It 
was  difficultly  soluble  in  water  and  melted  at  165°,  without 
effervescence.  The  pyrimidine  showed  a  strong  tendency  to 
occlude  water.  In  order  to  thoroughly  dry  it  for  analysis  it 
was  necessary  to  heat  for  about  i  hour,  at  115°-! 20°.  Analy- 
sis : 


1  86  Johnson  and  Johns. 

Calculated  for 

C5H5N3SClBr.  Found. 

N  16.50  16.38 

2-Methylmercapto-5-brom-4,6-diaminopyrimidine, 

N= 


CH3SC  CBr     .  —  This  derivative  was  prepared  by  heating 

II  II 

N  -  CNH2 

2-methylmercapto-4-chlor-5-brom-6-aniinopyrimidine  with 
aqueous  ammonia,  for  4  hours,  at  150°-!  60°.  When  the  tube 
was  opened  the  compound  had  separated  in  magnificent  prisms. 
Some  of  these  crystals  measured  3  cm.  in  length.  Thepyrim- 
idine  crystallized  from  hot  water  in  beautiful  prisms  and 
melted  at  192°,  to  a  clear  oil.  The  yield  corresponded  to  about 
80  per  cent  of  the  theoretical.  Analysis  (Kjeldahl)  : 

Calculated  for 
C6H7N4SBr.  Found. 

N  23.83  23.77 

An  attempt  was  made  to  prepare  this  diaminopyrimidine  by 
heating  the  2-methylmercapto-4-chlor-5-brom-6-aminopyrimi- 
dine  with  alcoholic  ammonia.  After  heating  for  4  hours,  at 
I5o°-i6o°,  it  was  recovered  unaltered.  The  alcohol  solution 
gave  only  a  faint  test  for  chlorine.  The  2-methylmercapto-5~ 
brom-4,6-diaminopyrimidine  is  very  stable  in  contact  with 
aqueous  and  alcoholic  ammonia,  at  higher  temperatures.  Af- 
ter heating  for  8  hours,  at  i8o°-i9O°,  with  concentrated, 
aqueous  ammonia,  it  was  recovered  unaltered.  It  was  again 
heated  with  fresh  aqueous  ammonia,  for  5  hours,  at  200°—  210°. 
Only  a  trace  of  mercaptan  could  be  detected  and  the  pyrimi- 
dine  was  recovered,  melting  sharply  at  192°.  A  similar  result 
was  obtained  when  it  was  heated  with  concentrated,  alcoholic 
ammonia,  for  4  hours,  at  2oo°-2i4°. 

N=   =CNH2 

I  I 

2-Thio-4-oxy-5-brom-6-aminopyrimidine,    CS        CHBr,   was 

NH  -  CO 


Researches  on  Pyrimidines.  187 

made  by  adding  a  molecular  proportion  of  bromine  to  an  acetic 
acid  solution  of  2-thio-4-oxy-6-aminopyrimidine.  It  separated 
from  the  acetic  acid  in  granular  crystals.  It  was  difficultly 
soluble  in  acetic  acid  and  insoluble  in  water.  It  did  not  melt 
below  300°.  Analysis  (Kjeldahl)  : 

Calculated  for 

C4H4ON3SBr.  Found. 

N  18.91  18.68 

2-Methylmercapto-£-anilido-6-aminopyrimidine, 
N=   =CNH2 

I  I 

CH3SC  CH  . — Four  grams  of  2-methylmercapto-4- 

II  II 

N CNHC6H5 

chlor-6-aminopyrimidine  were  heated  with  i  molecular  propor- 
tion of  aniline,  for  6  hours,  at  ioo°-i3o°.  A  clear,  red  var- 
nish was  obtained,  which  dissolved  in  boiling  alcohol.  Upon 
cooling,  rhombic-shaped  prisms  separated.  They  were  puri- 
fied by  recrystallizing  from  alcohol  and  melted  at  121°,  with 
violent  effervescence.  A  nitrogen  determination  agreed  with 
the  calculated  for  a  dihydrochloride  : 

Nz:   =CNH2 

I  I 

CH3SC  CH  .2HC1. 

II  II 

N CNHC6H5 

Calculated  for  Found. 

C]iHuN4SCl2.  I.  II. 

N  18.36  18.01  18.11 

The  free  pyrimidine  base  was  obtained  by  triturating  the  hy- 
drochloric acid  salt  with  an  excess  of  dilute  sodium  hydroxide. 
The  base  crystallized  from  benzene  in  clusters  of  microscopic 
prisms  and  melted  at  124°,  without  effervescence,  to  a  clear 
oil.  It  gave  a  strong  test  for  sulphur,  but  contained  no  chlo- 
rine. Analysis  (Kjeldahl)  : 

Calculated  for 
CnHuN4S.  Found. 

N  24.13  23.82 


1 88  Johnson  and  Johns. 

2,4.-Dianilido-6-aminopyrimidine) 
N=   =CNH2 

I  I 

C6H5NH.C  CH  .—Seven    grams    of    2-methylmer- 

N CNHC6H5 

capto-4-chlor-6-aminopyrimidine  were  heated  with  2  molecular 
proportions  of  aniline,  at  140°-!  50°,  for  10  hours.  A  slow 
effervescence  took  place  and  methylmercaptan  was  constantly 
given  off.  Upon  cooling,  the  reaction-product  hardened  to  an 
amorphous  solid.  This  was  treated  with  a  warm  solution  of 
sodium  hydroxide,  when  it  melted  to  a  heavy,  thick  oil.  The 
excess  of  aniline  was  then  removed  by  distillation  with  steam. 
On  cooling,  a  crystalline  cake  remained,  which  weighed  10 
grams.  This  pyrimidine  was  very  difficult  to  purify.  It  was 
extremely  soluble  in  cold  alcohol,  benzene  and  ether.  It  dis- 
solved in  hot  water,  but  separated,  on  cooling,  as  an  oil  which 
finally  solidified  to  a  hard,  amorphous  mass.  To  effect  puri- 
fication it  was  converted  into  its  sulphuric  acid  salt.  This 
salt  is  insoluble  in  cold  water.  When  warmed  with  water  it 
dissociates  into  the  free  base  and  sulphuric  acid.  It  can  be 
crystallized  from  alcohol  containing  free  sulphuric  acid.  It 
separated  from  alcohol  in  granular  crystals  and  melted  at  190°- 
193°,  with  effervescence.  Analysis  (Kjeldahl)  : 

Calculated  for 
Ci6H15N5.H2SO4.  Found. 

N  18.66  18.73 

The  pyrimidine  base  was  obtained  from  this  sulphuric  acid 
salt  by  warming  with  a  dilute  solution  of  ammonium  hydrox- 
ide. It  separated  as  an  oil,  which  finally  solidified  on  stand- 
ing. After  drying  over  sulphuric  acid  for  24  hours,  it  melted 
at  65°-7O°,  to  a  slightly  turbid  oil.  It  is  extremely  soluble  in 
the  ordinary  organic  solvents.  Analysis  (Kjeldahl)  : 

Calculated  for 

CieHi5N5.  Found. 

N  25.27  24.81 


Researclws  on  Pyrimi dines.  189 

2  -  Methylmercapto-4-parabromanilido-5-brom-6-aminopyrimi- 
N~ CNH2 

dine,  CH3SC  CBr  .  —  The    2-methylmercapto-4- 

II  II 

N CNHC6H4Br 

anilido-6-aminopyriraidine  was  dissolved  in  glacial  acetic  acid 
and  bromine  carefully  added,  as  long  as  the  bromine  color  dis- 
appeared. Stout  prisms  separated  immediately,  which  were 
difficultly  soluble  in  acetic  acid.  They  decompose,  with  vio- 
lent effervescence,  at  about  290°,  turning  somewhat  brown  at 
2io°-22o°.  A  nitrogen  determination  agreed  with  the  calcu- 
lated for  the  hydrobromic  acid  salt  of  a  dibrom-substitution- 
product : 

Calculated  for 

CnH11N4SBr3.  Found. 

N  11.89  12.29 

The  pyrimidine  base  was  obtained  by  treating  the  hydro- 
bromic acid  salt  with  a  10  per  cent  solution  of  sodium  hydrox- 
ide. It  melted  at  202°,  without  effervescence,  to  a  clear  oil. 
A  nitrogen  determination  agreed  with  the  calculated  for 
2-methylmercapto-4-bromanilido-5-brom-6-aminopyrimidine  : 

Calculated  for 

CiiH10N4SBr2.  Found. 

N  14-36  14.80 

In  order  to  establish  the  structure  of  this  dibrompyrimidine 
derivative  we  have  prepared  it  in  the  following  manner  :  3.6 
grams  of  2-methylmercapto-4-chlor-5-brom-6-aminopyrimidine 
were  heated  with  2.4  grams  of  parabromaniline,  for  4  hours, 
at  I2o°-i30°.  A  violet-colored  oil  was  obtained  which  solidi- 
fied on  cooling.  The  material  was  insoluble  in  water,  but 
soluble  in  hot  acetic  acid.  In  order  to  obtain  the  free  base  the 
substance  was  triturated  with  sodium  hydroxide,  filtered  and 
then  boiled  in  acetic  acid,  with  animal  charcoal,  to  remove  the 
color.  On  cooling,  long,  slender  prisms  were  obtained,  which 
melted,  without  effervescence,  at  202°.  When  some  of  this 
base  was  mixed  with  the  above  product,  obtained  by  bromina- 
ting  2-methylmercapto-4-anilido-6-aminopyrimidine  (m.  p. 


1 90  Johnson  and  Johns. 

202°),  the  melting-point  was  not  lowered.  Analysis  (Kjel- 
dahl)  : 

Calculated  for 

CnH10N4SBr2.  Found. 

N  14.36  14.31 

N=   =CNH2 

2-Oxy-4.-chlor-5-brom-6-aminopyrimidine,       CO        CBr     . — 

I  II 

NH CC1 

This  compound  was  obtained,  in  the  form  of  its  hydrobromic 
acid  salt,  when  2-oxy-4-chlor-6-aminopyrimidine  was  sus- 
pended in  glacial  acetic  acid  and  treated  with  i  molecular  pro- 
portion of  bromine.  The  hydrobromide  separated  as  an 
orange-colored  powder,  which  decomposed  at  23O°-24O°,  with 
effervescence.  In  order  to  obtain  the  free  base  the  crude  salt 
was  warmed  with  a  solution  of  dilute  sodium  hydroxide. 
When  the  alkali  solution  was  acidified  with  dilute  acetic  acid 
the  base  separated  as  a  crystalline  precipitate.  It  crystallized 
from  hot  water  in  clusters  of  microscopic  prisms  and  showed  no 
definite  melting-point,  but  began  to  turn  brown  at  210°  and 
decomposed  at  about  230°,  with  violent  effervescence.  Analy- 
sis : 

Calculated  for 

C4H3ON3ClBr.  Found. 

N  18.70  18.68 

Action  of  Aqueous  Ammonia  on  2-Ethylmercapto-6-chlorpyrimi- 

dine. 

At  1 4.0° -i 50° . — After  heating  with  aqueous  ammonia,  for  4 
hours,  at  140°- 150°,  the  pyrimidine  was  recovered  unaltered. 

At  J(?5°-J95°.  —  The  chlorpyrimidine  was  heated  with 
aqueous  ammonia,  for  3  hours,  at  185°— 195°.  The  ammoniacal 
solution  was  then  evaporated  to  dryness.  The  crystalline 
residue  was  warmed  with  alcohol  and  filtered  from  the  undis- 
solved  ammonium  chloride.  The  alcoholic  filtrate  was  then 
evaporated  to  dryness  and  the  residue  again  dissolved  in  water. 
The  chlorine  was  removed  by  precipitating  with  silver  sul- 
phate, then  the  sulphuric  acid  removed  with  barium  hy- 


Researches  on  Pyrimidines.  igi 

droxide  and  the  excess  of  barium  with  carbon  dioxide.  When 
the  solution  was  evaporated  to  dryness  we  obtained  a  crystal- 
line base  which  had  all  the  properties  of  2,6-diaminopyrimi- 
dine.  It  was  extremely  soluble  in  water.  The  base  was 
identified  by  means  of  its  platinum  chloride  salt.  Analysis  : 

Calculated  for 
(C4H6N4)2.H2PtCl6.  Found. 

Pt  (194-8)  30-9  30.5 

Action  of  Aqueous  Ammonia  on  2-Ethylmercapto-^-brom-6-chlor- 
pyrimidine.1 

At  i40°-i5O°. — When  the  pyrimidine  was  heated  with 
aqueous  ammonia,  at  i4o°-i5O°,  for  4  hours,  it  was  converted, 
quantitatively,  into  2-ethylmercapto-5-brom-6-aminopyrimi- 
dine,  melting  sharply  at  124°-! 25°. 

At  185°-! 95°.—  After  heating  for  4  hours,  at  i6o°-i7o°  and 
then  for  3  hours,  at  i85°-i95°,  the  2-ethylmercapto-5-brom-6- 
aminopyrimidine  was  again  obtained,  melting  at  124°-! 25°. 

NEW  HAVEN,  CONN., 
May  i,  1905. 

i  Wheeler  and  Johnson  :  Loc.  cit. 


.XXXIV.     No.  3. 

Septetii.  •' 


Contributions  from  the  Sheffield  Laboratory  of  Yale  University. 

CXXVI.— RESEARCHES  ON  PYRIMIDINES  :  2-ETHYI,- 
MERCAPTO-5-AMINO-6-OXYPYRIMIDINE. 

[ELEVENTH  PAPER.] 

BY  TREAT  B.  JOHNSON. 

The  work  described  in  this  paper  was  undertaken  with  the 
object  of  investigating  the  formation  and  properties  of  2-ethyl- 
mercapto-5-amino-6-oxypyrimidine.  The  examination  of  this 
pyrimidine  was  of  particular  interest  in  the  study  of  oxy- 
diaminopyrimidines,  because  it  offered  the  possibility  of  syn- 
thesizing both  2,5-diamino-6-oxypyrimidine  and  2-oxy-5,6- 
<Iiaminopyrimidine.  The  preparation  of  2,5-diamino-6-oxy- 
pyrimidine  from  this  mercaptopyrimidine  will  be  discussed  in 
a  later  paper. 

In  a  previous  paper3  from  this  laboratory,  it  was  shown  that 

2  Johnson  and  Clapp  :  THIS  JOURNAL,  33,  131  (1904). 


1 92  Johnson. 

ethyl  formate  condenses,  in  benzene,  with  ethyl  hippurate,  in 
the  presence  of  metallic  sodium,  to  form  the  sodium  salt  of 
formylethylhippurate.1  This  salt  condensed  very  readily  with 
pseudoethylthiourea  to  give  the  benzoyl  derivative  of  2-ethyl- 
mercapto-5-amino-6-oxypyrimidine.  Attempts  to  hydrolyze 
this  acyl  derivative  to  the  free  pyrimidine,  (V.),  were  unsuc- 
cessful. Acids  could  not  be  used  for  the  hydrolysis  on  account 
of  the  ease  with  which  the  mercapto  radical  was  displaced  by 
hydroxyl.  When  boiled  with  sodium  hydroxide  the  pyrimi- 
dine ring  was  opened,  to  form  a  sodium  salt  of  a-benzoyl- 
amino-/3-pseudoethylthioureaacrylic  acid  (I.).  This  acid  was 
unstable  and  immediately  condensed  again  to  the  pyrimidine, 
when  the  sodium  salt  was  treated  with  acids  : 

NH CO 

I  I                           NaOH 
C2H6SC           CNHCOC6H5 

II  II 
N CH 

NH2     NaOOC 

I  I 

C2H5SC  CNHCOCftH6. 

N CH 


I  now  find  that  ethyl  formate  condenses  very  smoothly,  in 
benzene,  with  carbethoxyaminoethylacetate,  in  the  presence  of 
metallic  sodium,  to  form  the  sodium  salt  of  formylcarbethoxy- 
aminoethylacetate  (II.)  : 

C2H5OOCNHCH2COOC2H5  +  HCOOC2H5  -f  Na     = 
C2H5OOCNHCCOOC2H5 

||  -f  C2H5OH  +  H, 

CHONa 
II. 

This  sodium  salt  condensed  at  the  ordinary  temperature,  in 
aqueous  solution,  with  pseudoethylthiourea,  giving  a-carbeth- 
oxyamino-/?-pseudoethylthioureaacrylic  acid  (III.).  The  yield 

1  Erlenmeyer,  in  his  recent  paper  on  the  synthesis  of  serin  andcystine,  has  shown 
that  this  salt  can  be  obtained  very  smoothly  by  condensing  ethyl  formate  with  ethyl 
hippurate,  in  alcohol,  by  means  of  sodium  ethylate.  Ann.  Chem.  (lyiebig),  337,  251. 


Researches  on  Pyrimidines.  193 

of  this  acid  corresponded  to  about  40-50  per  cent  of  the  theo- 
retical : 

NH2       COOC2H5 

II 
C2H5SC       -f  CNHCOOr         LH2O     = 


NH 

NH,     COOH 

CNHCOOC.H5  +  NaOH  +  C2H5OH. 

N-  -  CH 
ill. 

'.  succeeded  in  isolating  the  pyrimidine  — 

2-ethylmercaptc-5-carr         xyamino-6-oxypyrimidine,  (IV.)  — 
product  of  this  eo   iensation.     This  compound,  neverthe- 
ined  when  the  acrylic  acid  was  warmed 
h  acetic  ir        Aide. 
JOH 

acetic  anhydride 
CNHCOOC2H5  -f  —  * 

II 
N  -  CH 

NH  -  CO 

i  I 

C2H5SC  CNHCOOC2H5  +  H2O. 

II  II 

N  -  CH 
IV. 

When  this  pyrimidine,  (IV.)  was  boiled  with  a  solution  of 
sodium  hydroxide,  it  was  converted  into  2-ethylmercapto-5- 
amino-6-oxypyrimidine,  (V.)  : 
NH  -  CO 

I  I  H2O 
C2H5SC          CNHCOOC2H5     —  - 

II  II 
N  -  CH 

NH  --  CO 

I  I 

C2H5SC          CNH2  +  CO,  +  C2H5OH. 

II  II 
N  -  CH 

V. 


194  Johnson. 

The  formation  of  the  above  acrylic  acid,  (III.)  is  of  interest 
as  the  second  case  in  which  the  formation  of  intermediate  prod- 
ucts has  been  observed  in  the  preparation  of  pyrimidines  from 
pseudothioureas.  The  first  case  observed  was  described  by 
Johnson  and  Clapp,1  in  a  paper  on  the  preparation  of  2-amino- 
5-methyl-6-oxypyrimidine  from  guanidine  and  the  sodium  salt 
of  formylethylpropionate.  They  not  only  observed  the  forma- 
tion of  an  intermediate  acrylic  acid  in  this  condensation,  but 
also  were  able  to  show  that  it  was  capable  of  existing  in  two 
stereoisomeric  modifications. 

The  a-carbethoxyamino-/3-pseudoeihylthiourea  acrylic  acid 
(III.)  is  especially  characterized  by  its  stability  towards  cold 
alkali  solutions.  On  account  of  this  pronounced  stability  I 
have  designated  it  as  the  /rans-modification.  '  Under  the  ex- 
perimental conditions  I  used  I  did  not  succeed  in  isolating  an 
unstable  cw-modification. 

The  trans-acid  is  very  easily  decomposed  when  boiled  with 
strong  and  dilute  solutions  of  sodium  hydroxide.  When  it 
was  boiled  for  a  few  minutes,  with  a  strong  sodium  hydroxide 
solution  and  the  solution  then  neutralized  with  acids  or  car- 
bon dioxide,  it  was  converted,  almost  quantitatively,  into 
2-ethylmercapto-5-amino-6-oxypyrimidine  (V.)  : 

NH2     COOH 

I  I                              NaOH 
C2H5SC          CNHCOOC2H5 > 

II  II 
N CH 

NH CO 

I  I 

C2H5SC  CNH2  +  C2H5OH  +  CO2. 

II  II 
N CH 

V. 

This  interesting  saponifi cation  and  condensation  of  the  trans- 
acid  to  the  mercaptoaminopyrimidine,  (V.)  led  me  to  examine 
its  behavior  when  warmed  with  a  dilute  solution  of  sodium 

i  Loc.  cit. 


Researches  on  Pyrimidines.  195 

hydroxide.  The  experimental  data  at  hand  seem  to  indicate  that 
the  Zratw-acid  is  saponified  by  dilute  alkali  to  an  intermediate 
2-ethylmercapto-5-carboxylamrr  -oxypyrimidine,  (VI.). 

NH2     COOH 

I  I  Na 
C2H5SC          CNF^X)C2H5 

II  H 
N CH 

NH CO 


CNHCOOH  +  C2H5OH. 

II 


-OH 
VI. 

existence  ?  (     ^is  intermediate  carbamic  acid  is  particu- 

interestin0"  oecause  of  the  fact  that  it  contains  a  cyclic 

ide  linking.     Analogous  acids   in   the   acyclic  series 

>.-en  obtained  by  Fisher,1  in  his  important  researches  on 

.ypeptides.    The  relationship  between  the  above  pyrimidine, 

(VI.)  and  a  true  polypeptide  linking  is  made  evident  by  the 

following  comparison  : 

Acyclic  series. 

HN— CO— CH2— NH— COOH. 


Cyclic  series. 

HN— CO— C— NH— COOH 

I  II 

C2H6SC=N CH 

It  has  been  the  usual  experience,  during  the  investigation 
of  pyrimidines  in  this  laboratory,  to  find  that  a  mercaptooxy- 
pyrimidine  reacts  normally  with  phosphorus  oxychloride,  or 
phosphorus  pentachloride,  to  give  a  chlorpyrimidine  deriva- 
tive. It  has  also  been  observed  repeatedly  that  the  resulting 
chlorpyrimidines  are  obtained  combined  with  phosphorus  oxy- 
chloride. These  phosphorus  compounds  are  very  unstable  and 

1  Ber.  d.  chem.  Ges.,  36,  2094  (1903). 


196  Johnson. 

are  decomposed  by  water,  with  formation  of  the  free  chlor- 
pyrimidine.  I  now  find  that  2-ethylmercapto-5-amino-6-oxy- 
pyrimidine  reacts  with  phosphorus  oxychloride  to  form  a 
phosphorus  compound  which  is  abnormally  stable.  The 
analytical  determinations  agree  with  the  calculated  for  a  phos- 
phoryldichloride  derivative  (VII.)  : 

NH CO  N CC1 

I            1                  POC1,  I  I 

C2H5SC  CNH2          ^         C2H5SC  CNHPOC12. 

'    II  II  '    II  II 

N CH  N CH 

VII. 

This  phosphorus  derivative  could  be  warmed  with  water 
without  decomposition.  When  it  was  heated  with  alcoholic 
ammonia  2  chlorine  atoms  were  removed  and  a  stable  com- 
pound was  obtained,  which  I  have,  provisionally,  represented 
as  a  phosphoryltriamide  derivative,1  (VIII.)  : 


;2H5SC 


N- CC1 

I                       NH3 
CNHPOC12     1 

II 
N CH 


The  fact  that  this  amino  radical  should  show  such  pro- 
nounced affinity  for  phosphorus,  is  of  interest.  In  a  recent  com- 
munication from  this  laboratory2  it  has  been  shown  that  the  iso- 
meric2-ethylmercapto-4-oxy-6-aminopyrimidine  reacts  perfectly 
normally  with  phosphorus  oxychloride,  to  form  2-ethylmercapto- 
4-chlor-6-aminopyrimidine,  (IX.).  Furthermore,  Gabriel  and 

1  These  phosphoryl  pyrimidine  derivatives  will  receive  further  attention  in  this 
laboratory. 

J  Johnson  and  Johns  :  Preceding  paper. 


Researches  on  Pyrimidines.  197 

Colman1  have  shown  that  2-aniino-4-oxy-6-methylpyrimidine 
is  converted,  by  phosphorus  oxychloride,  into  2-amino-4-chlor- 
6-methylpyrimidine.  Later,2  they  observed  that  2-amino-6- 
oxypyrimidine  (isocytosine)  alsr  'eacts  normally  with  phos- 
phorus oxychloride,  to  give  2-amino  6-chlorpyrimidine,  (XI.). 


IN 

i^;rsi  M2 

i3 

i  • 

NH,C          CH    . 

"NT 

JN 

VJVJ1 

I 

C2H5SC 

II 
N- 

! 

CF 

jj 

!~~  CC1 

IX. 

1 

NH,.C 

II 

N- 

C 

II 

PTT 

X 

XL 

i  a  previous  pub!  Nuc!  .^saure  des  Weisen- 

,c  produced  evidence  to 

that,  in  triticoni,    etc  acid,  there  is  a  direct  union  be- 

the   nitrogen   of    the   purine  bases. 

at  _  ^olication,  has  produced   more  evidence 

_  tact  of  this  union  in  the  nucleic  acid  mole- 

Fur  Uiermore,  his  experiments  tend  to  show  that  it  is  the 

^_ii  atom  occupying  position  7  in  the  purine  molecule  that 

probably  joined  to  the  phosphorus.     It  is  of  interest  to  note, 

in  this  connection,  that  the  nitrogen  atom  in  the  aminopyrimi- 

dine,    (V.)  which  shows  such  affinity  for  phosphorus,   corre- 

sponds to  the  nitrogen  atom  occupying  position  7  in  the  purine 

molecule. 

iN  --  C6 


2C        sC—  N7 

|  | 

3N  --  C 


EXPERIMENTAL. 


Sodium  Salt  of  Formykarbethoxyaminoethylacetate, 
C2H5OOCNHC  :  (CHONa)COOC2H6.— The  carbethoxyamino- 
ethylacetate,  used  for  the  preparation  of  this  sodium  salt,  was 


1  Ber.  d.  chem.  Ges.,  32,  2921. 

2  Ibid.,  36,  3383. 

3  Z.  physiol.  Chem.,  36,  85  (1902). 

4  Ber.  d.  chem.  Ges.,  37,  708. 


198  Johnson. 

prepared  by  Fisher's1  method,  from  the  hydrochloride  of 
aminoethylacetate  and  chlorethylformate.  The  hydrochloride 
of  aminoethylacetate  was  prepared  according  to  Klages'2  direc- 
tions, from  methyleneaminoacetonitrile.  The  method  is  ex- 
tremely suitable  for  preparing  large  quantities  of  this  hydro- 
chloride.  Ethyl  formate  condenses  very  smoothly  with  carb- 
ethoxy aminoethylacetate,  in  the  presence  of  sodium,  in  either 
benzene  or  ether  ;  but  it  has  been  my  experience  that  the  con- 
densation is  much  smoother  and  more  rapid  when  benzene  is 
used  as  the  diluent.  This  sodium  salt  is  much  more  stable  in 
contact  with  the  air  than  the  sodium  salt  of  formylethylace- 
tate.  I  also  found  that  the  condensation  could  safely  be  ac- 
celerated by  gently  warming  the  benzene  solution  on  the 
steam-bath.  The  purity  of  the  salt  obtained  was  not  affected 
by  this  treatment.  In  all  my  condensations  the  yield  of  crude 
sodium  salt  has  been  about  equal  to  the  weight  of  carbetlioxy- 
aminoethylacetate  used. 

Trans-a-carbethoxyamino-fi-pseiidoethylthiourea  Acrylic  Acid. 

C2H5OOC.NH— C— COOH 

||  . — Twenty-five  grams  of  the 

H2N.  (C2H5S)C=N— CH 

sodium  salt  of  formylcarbethoxyaminoethylacetate  were  dis- 
solved in  water  and  added  to  an  aqueous  solution  of  pseudo- 
ethylthiourea,  which  was  previously  prepared  by  treating  17 
grams  of  pseudoethylthiourea  hydrobromide  with  6  grams  of 
potassium  hydroxide.  The  clear  solution,  which  resulted,  was 
then  allowed  to  stand  for  a  few  hours,  at  the  ordinary  temper- 
ature. Upon  neutralizing  with  acetic  acid  a  beautiful,  white, 
crystalline  compound  separated.  It  was  insoluble  in  alcohol  and 
cold  water.  It  could  be  dissolved,  repeatedly,  in  cold  solutions 
of  sodium  hydroxide  and  be  precipitated,  unaltered,  by  acids. 
It  was  purified  for  analysis  by  recrystallizing  from  hot  water. 
It  separated  as  a  colorless  powder,  consisting  of  microscopic 
prisms.  It  showed  no  sharp  melting-point  but  decomposed, 
with  effervescence,  at  259°.  A  yield  of  1 1 . 5  grams  of  crude 
material  was  obtained.  For  analysts  it  was  dried  at  100°. 

1  Ber.  d.  chem.  Ges.,  36,  2107. 
» Ibid.,  36,  1508. 


Researches  on  Pyrimidines.  199 

0.1574  gram  substance  gave  0.1341  gram  BaSO4  (Carius). 

Calculated  for 


Found. 

N  16.00  15.75 

S  12  a  11.70 

The  following  table  i«*      ;-en  to  show  the  comparative  yields 
obtained  in  four  di^      m  preparation-  of  this  trans-acid  : 

Table. 


Weight  of  carbeth- 
oxyatn; 
ac*-    ,1e  used. 

Weig> 

on    •• 
-product 

'It  Of 

trans-Add. 

Percentage  of 
theoretical. 

Grams. 

Grams. 

Grams. 

Per  cent. 

30 

40 

20 

25 

*i-5 

46 

45  - 

20.0 

45 

40 

••45 

19-5 

44 

:dibethoxyamino-6-oxypyrimidine, 

' 

, 
CNHCOOC2H5.— This  compound  was  easily  ob- 

,i  I! 

N CH 

tained  when  the  trans-acid,  above  described,  was  dissolved  in 
warm  acetic  anhydride.  On  adding  water  the  pyrimidine 
separated  in  prisms.  It  was  easily  purified  by  recrystallizing 
from  15  per  cent  acetic  acid  and  separated,  on  cooling,  in  well- 
developed  prisms,  which  melted,  without  effervescence,  at  189°- 
190°,  to  a  clear  oil.  The  pyrimidine  dissolves  in  sodium  hy- 
droxide solution  and  is  reprecipitated,  unaltered,  by  acids.  It 
was  also  obtained,  in  an  impure  condition,  when  the  trans-acid 
was  boiled  with  glacial  acetic  acid.  Analysis  : 

Calculated  for 
C9H13O3N3S.  Found. 

N  17.28  17.35 

2-Ethylmercapto-5-amino-6-oxypyrimidine, 
NH CO 

C2H5SC  CNH2. — Ten  grams  of  the  trans-acid  were  dis- 

II  II 

N CH 

solved  in  50  cc.  of  water,  containing  5  grams  of  sodium  hydrox- 


2OO  Johnson. 

ide.  The  alkaline  solution  was  boiled  for  about  20  minutes 
and  then  allowed  to  stand  for  30  minutes.  When  the  alkaline 
solution  was  made  slightly  acid  with  acetic  acid  the  pyrimidine 
separated  in  beautiful,  needle-like  crystals,  which  melted,  to  a 
clear  oil,  at  about  155°.  It  was  purified  by  recrystallizing 
from  hot  water.  It  separated  in  clusters  of  radiating  needles 
and,  without  effervescence,  melted  at  160°,  to  a  clear  oil.  The 
yield  was  practically  quantitative.  This  pyrimidine  was  also 
formed  when  2-ethylmercapto-5-carbethoxyarnino-6-oxypyrimi- 
dine  was  boiled  with  sodium  hydroxide.  Analysis  (Kjeldahl)  : 

Calculated  for 
C6H9ON3S.  Found. 

N  24.56  24.34 

Disilver  Salt  of  2-Ethylmercapto-5-carboxylamino-6-oxypyrimi- 
N COAg 

I  I 

dine,  C2H5SC  CNHCOOAg.— The  acid  of  this  salt  was  ob- 

it II 

N CH 

tained,  in  solution,  from  two  different  preparations  of  the  trans- 
acid.  It  was  formed  by  boiling  the  latter  with  a  dilute  solution  of 
sodium  hydroxide.  It  was  very  soluble  in  water  and  was  not 
precipitated  from  the  alkali  solution  by  mineral  acids  or  car- 
bon dioxide.  The  disilver  salt  was  obtained,  after  acidifying 
the  alkaline  solution  with  nitric  acid,  by  adding  a  slight  ex- 
cess of  20  per  cent  silver  nitrate  solution.  The  salt  was  diffi- 
cultly soluble  in  water  and  showed  no  crystalline  form. 
Analysis  of  the  substance,  thoroughly  dried  over  sulphuric 
acid  : 
o.  1399  gram  silver  salt  gave  0.0707  gram  metallic  silver. 

Calculated  for 

CTH7O3N3SAg2.  Found. 

Ag  5°- 35  50-53 

2-Ethylmercapto-5-phosphoryldichloramino-6-chlorpyrimidine, 

N 


>2H5SC 


CNH.POC1,.— Four   and  eight- tenths  grams  of 

II  II 

N CH 


Researches  on  Pyrimidines.  201 

2-ethylmercapto-5-amino-6-oxypyrimidine  were  warmed,  on  a 
sand-bath,  with  an  excess  of  phosphorus  oxychloride.  A  re- 
action set  in  at  once,  with  f  'ution  of  hydrochloric  acid  gas. 
After  this  ceased  the  excess  of  phosphorus  oxychloride  was 
removed  by  distillation  under  '.Uminished  pressure.  I  obtained 
a  yellow,  amorphou  residue.  Wh«.  n  this  was  treated  with 
water  very  litt1  vas  evolved  and  a  yellow,  crystalline  de- 

posit remai-  >d  suspended  in  the  water.     This  residue  was  fil- 
tered a*"d  then  warmed  with  water  on  the  steam-bath,  to  de- 
strov  any  phosphorus  oxychloric'        A  thick,  oily  product,  in- 
soluble in  water,  was  obtained  by  this  treatment ;  it  imme- 
iately  solidified,  on  coolr  _;    to  a  hard,  crystalline  cake.     It 
was   insoluble    in    the   •. d  nary    organic    solvents     and    also 
in    ammonium    hydroxide.      When    treated    with    a    solu- 
tion of  sodium   lr.  ••  oxide   it   showed    a  very  peculiar    be- 
.uct  was  insoluble  in  sodium  hydroxide,  but 
r  unc5  .rwent  decomposition  and  the  solution  assumed 
k  green  color.     It  gave  strong  tests  for  sulphur  and  phos- 
arus.     It  had  no  sharp  melting-point,  but  decomposed  at 
about  247°-25o°.     Analysis  : 

Calculated  for 

C6H7ON3SC13P.  Found. 

N  13.70  13.41 

2-Ethylmercapto-5-phosphoryltriamino-6-chlorpyrimidine, 

N — CC1 

|  I  /NH, 

C2H5SC  CNHPO<T  . — This     complicated    derivative 

II  II  XNH2 

N CH 

was  obtained  when  the  above  chloride  was  heated  with  alco- 
holic ammonia,  for  3  hours,  at  i6o°-i65°.  When  the  tube 
was  opened  there  was  no  pressure  and  only  a  slight  odor  of 
mercaptan  was  noticeable.  The  pyrimidine  was  suspended  in 
the  alcohol  and  had  a  green,  metallic  appearance.  It  was  in- 
soluble in  water  and  the  ordinary  organic  solvents.  It  gave 
strong  tests  for  chlorine,  sulphur  and  phosphorus.  It  had  no 
characteristic  melting-point,  but  began  to  sinter  at  about  258° 
and  decomposed  ?9o°-3OO°,  according  to  the  rate  of  heating. 
Analysis  : 


202  Johnson. 

Calculated  for 

C6HnON5SClP.  Found. 

N  26.16  26.12 

Sodium  Salt  of  a-Benzoylamino-p-pseudoethylihiourea  Acrylic 
Acid,  H2N(C2H5S)C  :  NCH  :  C(NHCOC6H5)COONa.  - 
This  salt  was  obtained  when  2-ethylmercapto-5-benzoylamino- 
6-oxypyrimidine1  was  boiled  with  a  solution  of  sodium  hydrox- 
ide. The  sodium  salt  separated,  on  cooling,  in  needles.  It 
crystallized  from  alcohol  in  needles  and  melted,  with  efferves- 
cence, at  i24°-i25°.  When  treated  with  acids  it  was  con- 
verted into  the  unaltered  pyrimidine,  melting  at  239°.  Analy- 
sis . 

Calculated  for 

sO.  Found. 


N  12.  61  12.45 

2-Ethylmercapto-5-benzalamino-6-oxypyrimidine, 
NH  -  CO 

I  I 

C2H5S.C  CN  :  CHC6H5.—  One  gram  of  2-ethylmercapto-5- 

II  II 
N  -  CH 

amino-6-oxypyrimidine  was  warmed  with  i  molecular  propor- 
tion of  benzaldehyde,  for  1-2  hours,  at  i6o°-i8o°.  Water  was 
given  off  immediately  on  warming  and  the  material  solidified 
to  a  crust  in  the  hot  bath.  The  pyrimidine  crystallized  from 
alcohol  as  a  microscopic  powder,  from  benzene  in  beautiful, 
rhombic  plates  or  flattened  prisms,  melting  at  185°-  187°,  to  a 
clear  oil.  By  prolonged  boiling  with  water  or  dilute  alcohol 
it  was  slowly  decomposed  into  benzaldehyde  and  the  unaltered 
pyrimidine.  Analysis  : 

Calculated  for 
Ci3Hi3ON8S.  Found. 

N  l6.2I  l6.00 

2-Thio-5-benzoylamino-6-oxypyrimidine, 
NH  -  CO 

CS        CNHCOC6H5.  —  Two  grams  of  thiourea  and   10  grams 

I  II 

NH  --  CH 

1  Johnson  and  Clapp  :  Loc.  cit. 


Researches  on  Pyrimidines.  203 

of  the  sodium  salt  of  formylethylhippurate1  were  dissolved  in 
50  cc.  of  water  and  warmed,  on  the  steam-bath,  for  about  20 
minutes.  The  solution  assumed,  at  once,  a  turbid  appear- 
ance, due  to  the  separation  of  ylhippurate.  Upon  cooling, 
a  small  amount  of  crystal1'  material  separated  from  the  alka- 
line liquid.  This  w^  emoved  by  filtration  and  dried  on  the 
oven.  No  further  pr<  »  ,-ipitate  was  obtained  when  the  alkaline 
solution  wa?  acidifie  vlth  acetic  aci  The  crystalline  prod- 
uct was  purified  b  cetic  acid.  It  separ- 

ated in  plates  -o°,  according  to  the 

diuni  hydroxide  and  was 

it  was  insoluble  in  water 

aed  with  hydrochloric  acid  it 

^tion  of  hydrogen  sulphide.     Analy- 


Calculated  for 
CnH9OjN3S.  Found. 

ly.OO  16.86 

2-Ethylmercapto-5,6-(t*-phenyloxazoline)pyrimidine    (By    S. 
N=   =C 


H.  Clapp),  C2H5SC  C— N^  * .  —  N  i  n  e    grams    of 

II  II 

N CH 

2-ethylmercapto-5-benzoylamino-6-oxypyrimidine1  were  heated 
to  boiling  with  50  cc.  of  phosphorus  oxychloride,  for  3  hours. 
Hydrochloric  acid  was  evolved  continuously.  The  excess  of 
phosphorus  oxychloride  was  then  distilled  off  under  diminished 
pressure.  I  obtained  a  thick  varnish,  which  would  not 
solidify.  This  was  treated  with  cold  water,  to  destroy  any 
excess  of  phosphorus  oxychloride.  Heat  was  evolved  and  a 
white,  crystalline  solid  separated.  This  was  thoroughly 
washed  with  water  and  purified  by  recrystallizing  from  alco- 
hol. It  melted,  without  effervescence,  at  io8°-iO9°  to  a  clear 
oil.  It  was  free  from  chlorine.  Analysis  (Carius)  : 
0.1399  gram  substance  gave  0.1268  gram  BaSO4. 

1  Johnson  and  Clapp  :  Loc.  cit. 


204  Researches  on  Pyrimidines* 

Calculated  for 
Ci3HnN3OS.  Found. 

S  12.45  12.43 

The  compound  was  insoluble  in  sodium  hydroxide  and  could 
be  boiled  with  alkali  without  decomposition.  When  warmed 
for  a  short  time  with  hydrochloric  acid  it  was  converted  into 
the  unaltered  2-ethylmercapto-5-benzoylamino-6-oxypyrimi- 
dine,  melting  at  238°-239°.  When  it  was  suspended  in  dry 
benzene  and  the  benzene  saturated  with  dry  hydrochloric  acid 
gas,  the  hydrochloride  was  formec1,  melting,  with  violent  ef- 
fervescence, at  147°.  When  this  salt  was  warmed  with  water 
it  underwent  dissociation  and  the  ox^7oline  was  recovered. 
Some  of  the  hydrochloric  acid  salt  was  heated  in  a  sealed  tube, 
with  alcoholic  ammonia,  for  2  hours,  at  ioo°-iio°.  The  alco- 
holic solution  was  evaporated  to  dryness  and  then  treated  with 
water,  to  remove  ammonium  chloride.  The  insoluble  residue 
proved  to  be  the  unaltered  oxazoline,  melting  at  io8°-io9°. 

The  close  relationship  between  our  oxazoline  and  /x-phenyl- 
oxazoline,  which  was  prepared  by  Gabriel  and  Heyman,1  is 
shown  by  the  following  formulae  : 

N=   =C— (X 
|  |         ^CPAGO  CH.-CX 

C2H6SC          C— N^  ,  |  \CC6H6O). 

||  ||  CH2— N^ 

N CH 

NEW  HAVBN,  CONN., 
May  6,  1905. 

1  Ber.  d.  chem.  Ges.,  33,  2495. 


[Reprinted  from  the  American  Chemical  Journal.    Vol.  XXXIV.     No.    6 
December,  1905.] 


Contributions  from  the  Sheffield  Laboratory  of  Yale  University. 

CXXVIL—  RESEARCHES  ON  PYRIMIDINES  :    ON  2,5- 

DIAMINO-6-OXYPYRIMIDINE. 

[TWELFTH  PAPER.] 

BY  TREAT  B.  JOHNSON  AND  CAKL  O.  JOHNS. 

In  a  paper  by  Wheeler  and  Johnson1  on  5-methylcytosine  it 
wras  stated  that  work  on  the  preparation  of  oxydiaminopyrimi- 
dines  would  be  carried  on  in  this  laboratory.  These  particular 
pyrimidine  derivatives  are  of  especial  interest  because  of  the 
fact  that  Kutscher2  believes  he  isolated  such  a  compound,  in  the 
form  of  its  picrate,  from  yeast  nucleic  acid.  Kutscher  consid- 
ers that  a  similar  analogy  exists  between  his  unknown  base 
and  cytosine  as  exists  between  thymine  and  uracil.  While 
thymine  differs  from  uracil  by  a  methyl  radical,  he  thinks  that 
his  new  base  differs  from  cytosine  by  an  amino  group. 

The  pyrimidine  derivatives  that  have  hitherto  been  isolated 
from  the  decomposition-products  of  nucleic  acid  have  been 
mono-oxy  or  di-oxy  derivatives,  in  which  the  oxygen  atoms  oc- 
cupy position  2  as  in  cytosine,  I.,  or  both  positions  2  and  6  as 
in  uracil,  II.,  and  thymine,  III.  : 

Nz:    =CNH2  NH CO  NH CO 

1  I  I  I  I 

:o      CH  co      CH         co      CCHS 

I       II  I       II          I       II 

NH CH  NH CH  NH CH 

I.  II.  III. 

THIS  JOURNAL,  31,  592  (1904). 
2,.  physiol.  Chem.,  38,  176  (1903). 


2 , 5-Diamino-6-oxypyrimidine.  555 

It  appears  to  the  writers  that  if  Kutscher'sbaseis  an  oxydi- 
aminopyrimidine,  of  all  the  possible  diamino  derivatives,  the 
most  probable  forms  to  be  considered  are  likewise  those  in 
which  the  oxygen  atom  occupies  either  position  2  or  6.  An 
examination  of  the  following  formulas  will  show  that  the  only 
oxydiamino  derivatives  that  fulfil  these  conditions,  assuming 
that  the  amino  groups  are  attached  to  carbon,  are  :  6-oxy- 
2,4-diaminopyrimidine,  IV.,  2-oxy-4,6-diaminopyrimidine,  V., 
6-oxy-2,5-diaminopyrimidine,  VI.,  and  2-oxy-5,6-diamino- 
pyrimidine,  VII.  : 

NH CO  N=   =CNH2 

II  II 

H2NC  CH  CO         CH 

II  II  I  II 

N CNH3  NH CNH2 

IV.  V. 

NH CO  N=   =CNH2 

II  II 

H2NC  CNH2  CO        CNH2 

I  II 

NH CH 

VII. 

Furthermore,  since  Kutscher  obtained  his  base  by  hydrolyz- 
ing  nucleic  acid  with  sulphuric  acid,  at  a  high  temperature  and 
under  pressure,  it  is  evident  that  the  only  forms  which  need  to 
be  considered  in  the  above  series  are  those  which  are  capable 
of  undergoing  the  same  treatment  without  complete  decompo- 
sition. 

Three  of  the  pyrimidines  represented  above  have  now  been 
synthesized  :  2,4-diamino-6-oxypyrimidine,  IV.,  has  been 
prepared  by  Traube.  *  He  obtained  it  by  condensing  guanidine 
with  ethyl  cyanacetate  in  presence  of  sodium  ethylate.  That 
this  derivative  cannot  be  the  compound  obtained  by  Kutscher 
is  established  by  the  fact  that,  when  it  is  heated  with  20  to  30 
per  cent  sulphuric  acid,  at  i3o°-i4o°,  it  is  completely  decom- 
posed. 

Wheeler  and  Jamieson2  have  described  2-oxy-4,6-diamino- 

1  Ber.  d.  chem.  Ges.,  33,  1371. 

2  THIS  JOURNAL,  32,  343  (1904). 


556  Johnson  and  Johns. 

pyrimidine,  V.  Their  experimental  evidence  excludes  the 
possibility  of  this  pyrimidine  being  identical  with  Kutscher's 
base.  It  was  easily  hydrolyzed  to  barbituric  acid  when  boiled 
with  mineral  acids. 

In  this  paper  we  shall  describe  the  preparation  and  proper- 
ties of  the  diamino  derivative  represented  by  Formula  VI., 
viz.:  2,5-diamiuo-6-oxypyrimidine.  We  have  prepared  this 
pyrimidine  by  three  different  methods,  as  follows  :  When  iso- 
cytosine1  was  nitrated  in  the  presence  of  strong  sulphuric  acid 
it  was  converted,  practically  quantitatively,  into  2-amino-5- 
nitro-6-oxypyrimidine,  VIII.  : 

NH CO 

I  I  HNO3 

H2NC  CH '-+ 


When  this  nitropyrimidine  was  reduced  in  an  ammoniacal 
solution  with  aluminium  amalgam,  it  was  converted,  smoothly, 
into  2,5-diamino-6-oxypyrimidine,  IX.  : 

NH CO  NH CO 


H3NC  CNO2  +  3H,       =       H2NC  CNH2  +  2H2O. 


IX. 

The  same  pyrimidine  was  also  formed  when  2-ethylmercapto- 
5-amino-6-oxypyrimidine2  was  heated  with  alcoholic  ammonia. 

NH CO  NH CO 

C2H5SC  CNH2  +  NH3   =   H2NC  CNH2  +  C2H5SH. 

II            II                                       II  II 

N CH  N CH 

The  third  method  which  has  served  for  the  preparation  of 
the  pyrimidine  was  by  heating  bromisocytosine3  with  concen- 
trated, aqueous  ammonia. 

1  Wheeler  and  Johnson  :  THIS  JOURNAL,  29,  493  (1903). 

2  Johnson  :  THIS  JOURNAL,  34,  191  (1905). 

3  Wheeler  and  Johnson  :  Loc.  cit. 


2 , 5-D  'amino-6-oxypyrimidine.  557 

NH CO  NH CO 

II  II 

H2NC  CBr  +  2NH3      =     H2NC  CNH2  +  NH4Br. 

II             II                                            II  II 

N CH  N CH 

Of  the  three  methods  of  preparation  the  first  is  the  only  one 
which  is  of  practical  value  for  the  production  of  the  base. 

We  now  find  that  this  2,5-diarnino-6-oxypyrimidine  agrees 
in  its  chemical  behavior,  so  far  as  we  are  able  to  judge,  with 
the  base  which  Kutscher  isolated  from  yeast.  Kutscher's 
meagre  description  of  his  base  makes  it  impossible  for  us  to  es- 
tablish with  preciseness  the  identity  of  the  two  compounds. 
It  is  the  first  one  of  the  above  series  of  four  pyrimidines  which 
we  have  been  able  to  heat  with  sulphuric  acid  without  com- 
plete decomposition.  Approximately  50  per  cent  of  the 
pyrimidine  was  recovered  unaltered,  after  heating  with  20  per 
cent  sulphuric  acid,  at  I3O°-I4O°.  Part  of  the  base  was  hy- 
drolyzed  by  this  treatment  to  a  difficultly  soluble  derivative, 
which  we  have  identified  as  2-ainino-5,6-dioxypyrimidine,  X. 
Under  the  conditions  employed  in  our  work  we  did  not  observe 
the  formation  of  aminouracil. 

NH  —  CO  NH — CO 

II  II 

H.NC  CNH2  +  HaO     =     H2NC  CO  +  NH8. 

II  II  II  I 

N CH  N CH2 

x. 

This  hydrolysis  is  perfectly  analogous  to  the  formation  of 
oxyuracil,  XI.,  from  aminouracil,  which  was  described  by 
Behrend.' 

NH CO  NH CO 

II  II 

CO         CNH2  -f  H2O     ==     CO         CO  -f  NH3. 

I             II                                    II 
NH CH  NH CH2 

XI. 
2,5-Diaraino-6-oxypyrimidine  crystallizes  from  water  with  i 

1  Ann.  Chem.  (I^iebig),  229,  40. 


558  Johnson  and  Johns. 

molecule  of  water  of  crystallization.  Analogous  to  Kutscher's 
base  it  gives  a  picrate  which  is  extremely  insoluble  in  water. 
Notwithstanding  its  insolubility,  it  is  not  a  derivative  suitable 
for  identifying  the  base  on  account  of  its  indefinite  decomposi- 
tion-point and  poor  crystalline  form.  The  base  also  forms  a 
beautiful  crystalline  series  of  salts  with  nitric,  hydrochloric 
and  sulphuric  acids. 

Kspecially  interesting  in  connection  with  the  nitration  of  iso- 
cytosine  was  the  behavior  of  its  benzal  derivative,  XII. ,  to- 
wards nitric  acid : 

NH CO 

I  I 
C6H5CH  :  NC           CH. 

II  II 
N CH 

XII. 

While  isocytosine  nitrates  vary  easily,  to  give  the  2-amino- 
5-nitro-6-oxypyrimidine,  VIII,  its  benzal  derivative  could  be 
recovered  unaltered  after  warming  with  a  mixture  of  nitric 
acid  (sp.  gr.  1.5)  and  concentrated  sulphuric  acid,  for  24 
hours. 

On  account  of  their  close  structural  relationship,  it  might  be 
expected  that  2-amino-6-oxypyrimidine,  XIII,  would  show 
some  analogy  in  its  chemical  behavior  to  a  3-pyrazolone,  XIV., 
or  a  5-pyrazolone,  XV.  : 

NH CO  NH CO  RN CO 

I 


H2NC  CH 


CH 


CH 


N CH          RN CR'  NH CR' 

XIII.  XIV.  XV. 

Wheeler  and  Bristol1  have  shown  that  when  pyrimidine  de- 
rivatives, having  hydrogen  both  in  positions  4  and  5,  are  at- 
tacked by  halogens  or  nitric  acid,  it  is  the  hydrogen  atom  in 
position  5  which  is  substituted.  The  3-pyrazolones2  and 
5-pyrazolones3  are  also  readily  attacked  by  halogens,  the  sub- 

1  THIS  JOURNAL,  33,  438  (1905). 

2  Ber.  d.  chem.  Ges.,  38,  154. 

3  Knorr  and  Duden  :  Ibid.,  25,  766. 


2,5-Diamino-6-oxypyrimidine.  559 

stitution  taking  place  in  position  4,  which  corresponds  to  posi- 
tion 5  in  the  pyrimidine  ring.  They  also  react  smoothly,  in 
acetic  acid,  with  sodium  nitrite  to  form  characteristic,  green- 
colored  nitroso  derivatives.  We  now  find  isocytosine  does  not 
react  with  nitrous  acid  ;  it  was  recovered  unaltered  after  re- 
maining in  a  nitrous  acid  solution  for  several  hours.  We  did 
not  observe  the  formation  of  any  uracil. 

Work  on  the  preparation  of  2-oxy-5,6-diarninopyrimidine  is 
in  progress  in  this  laboratory. 

EXPERIMENTAL. 

NH CO 

2- Amino-5-nitro-6-oxy pyrimidine,    H2NC  CNO2. — This 

II  II 

N CH 

nitro  derivative  was  prepared  by  nitrating  isocytosine.1  After 
several  experiments,  in  which  we  used  varying  proportions  of 
nitric  and  sulphuric  acids,  we  observed  that  we  obtained  the 
best  results  when  we  worked  under  the  following  conditions  : 
Six  grams  of  isocytosine  were  slowly  added  to  a  mixture  of  18 
cc.  of  nitric  acid  (sp.  gr.  1.5)  and  18  cc.  of  concentrated  sul- 
phuric acid.  The  nitration  was  very  violent  and,  in  order  to 
avoid  oxidation,  the  temperature  of  the  acid  mixture  was  not 
allowed  to  rise  above  100°.  After  the  final  addition  of  isocy- 
tosine the  mixture  was  heated  on  the  steam-bath  for  i 
hour,  to  complete  the  reaction.  Longer  heating  tends  to  di- 
minish the  yield  of  the  nitro  product.  The  acid  mixture  was 
thoroughly  cooled  and  poured  into  100  cc.  of  ice- water. 
The  clear  yellow  solution  that  resulted  was  then  made  slightly 
alkaline  with  ammonium  hydroxide.  On  cooling  we  obtained 
a  beautiful,  yellow,  crystalline  precipitate.  It  was  very  diffi- 
cultly soluble  in  hot  water,  from  which  it  separated,  on  cool- 
ing, in  clusters  of  microscopic  prisms.  It  was  insoluble  in  all 
the  ordinary  organic  media.  It  was  purified  for  analysis  by 
boiling  with  glacial  acetic  acid.  It  had  no  definite  decomposi- 
tion point,  but  began  to  turn  brown  at  about  280°  and  did  not 
decompose  below  300°.  The  yield  corresponded  to  92  per  cent 

1  Wheeler  and  Johnson  :  Loc.  cit. 


560  Johnson  and  Johns. 

of  the  theoretical.  A  nitrogen  determination,  by  KjeldahPs 
method,  gave : 

Calculated  for 

C4H4O3N4.  Found. 

N  35-89  35-70 

In  order  to  establish  the  structure  of  this  nitropyrimidine,  it 
was  heated  with  20  per  cent  sulphuric  acid,  for  4  hours,  at 
i9O°-2oo°.  When  the  solution  was  examined  a  beautiful  crys- 
talline solid  had  separated,  which  had  all  the  properties  of 
nitrouracil.  In  order  to  prove  that  this  was  nitrouracil  it  was 
reduced  to  aminouracil  with  aluminium  amalgam,  in  an  ammo- 
niacal  solution.  That  aminouracil  was  the  product  of  the  re- 
duction was  established  by  a  determination  of  nitrogen  in  the 
free  base  and  by  means  of  its  picrate.  The  picrate  showed 
signs  of  decomposing  at  147°  and  then  decomposed,  with  vio- 
lent effervescence,  at  245°-247°.1  A  determination  of  nitrogen 
in  the  free  base  gave  the  following  result : 

Calculated  for 
C4H5O2N3.  Found. 

N  33.07  32.99 

NH CO 

2,5-Diammo-6-oxypyrimidine,  H2NC  CNH2.H2O. — Five 

II  II 

N CH 

grams  of  2-amino-5-nitro-6-oxypyrimidine  were  suspended  in 
150  cc.  of  water,  to  which  5  cc.  of  14  per  cent  ammonium  hy- 
droxide solution  had  been  added.  To  this  ammoniacal  solu- 
tion was  then  added  an  excess  of  aluminium  amalgam  and  the 
temperature  of  the  solution  being  kept  below  40°  during  the 
reduction.  The  reduction  was  allowed  to  proceed  for  24  hours, 
when  the  aluminium  hydroxide  was  filtered  off.  We  obtained 
a  clear,  wine-colored  solution,  which  was  concentrated  on  the 
steam-bath  to  about  15  cc.  Decomposition  took  place  during 
this  evaporation  and  a  brown,  amorphous  substance  continued 
to  form  during  prolonged  heating.  The  concentrated  solution 
was  filtered  and  allowed  to  stand  over  night.  In  the  morning 
1.5  grams  of  crystalline  material  had  separated.  The  crystals 

1  Wheeler  and  Bristol :  THIS  JOURNAL,  33,  438  (1905). 


e.  561 

were  badly  etched  and  were  developed  in  the  form  of  large, 
radiating  prisms.  Associated  with  these  prisms  was  a  small 
amount  of  amorphous  material.  Some  of  the  large  prisms 
were  removed,  washed  with  cold  water  and  dried  in  the 
air.  The  water  of  crystallization  was  determined  at  I2O°-I3O°. 
0.2368  gram  substance  lost  0.0305  gram. 

Calculated  for 

C4HcON4.H2O.  Found. 

H2O  12.50  12.88 

The  anhydrous  base  had  no  definite  melting-point.  It  de- 
composed, with  slow  effervescence,  at  about  245°.  Analysis 
(Kjeldahl)  : 

Calculated  for 

C4H<jON4.  Found. 

N  44.44  43.96 

2,5-diamino-6-oxypyrimidine  is  extremely  soluble  in  water. 
When  boiled  with  water  the  solution  assumes  a  red  color  and 
the  base  apparently  slowly  oxidizes,  with  separation  of  a  floc- 
culent,  amorphous  residue.  It  is  a  strong  di-acid  base  and 
forms  a  very  characteristic  series  of  salts  (see  below)  with  ni- 
tric, hydrochloric  and  sulphuric  acids.  Of  these  three  salts  the 
nitrate  and  hydrochloride  are  very  soluble  in  water.  The  sul- 
phuric acid  salt  is  difficultly  soluble  in  water  and  is  the  most 
characteristic  derivative  of  the  base  that  we  have  obtained. 
The  base  is  precipitated  by  phosphotungstic  acid  and  mercuric 
chloride.  When  solutions  of  platinum  chloride  and  gold  chlor- 
ide were  added  to  an  aqueous  solution  of  the  base  no  double 
salts  separated,  but  the  halides  were  slowly  reduced  to  metallic 
platinum  and  gold.  With  potassiobismuth  iodide  the  base 
gives  a  brick-red  precipitate. 

The  picrate  was  formed  when  picric  acid  was  added  to  a  di- 
lute, aqueous  solution  of  the  base.  It  was  very  difficultly  sol- 
uble in  water.  It  separated  from  hot  water  in  aggregates  of 
short,  distorted  prisms  (Fig.  I.).  Traces  of  impurities  modify 
the  crystal  forms  of  the  salt.  Using  a  pure  sample  of  the  base 
the  picrate  separated  in  the  form  of  stout  needles.  The  picrate 
had  no  definite  decomposition-point,  but  decomposed  at  250°- 
300°,  according  to  the  rate  of  heating.  Analysis  : 


562  Johnson  and  Johns. 

Calculated  for 
C4H6N04.CeH307N8.  Found. 

N  27.60  27.58 

The  dihydrochldride,  C4H6ON4.2HC1.H2O,  was  prepared  by 
dissolving  the  base  in  warm,  concentrated  hydrochloric  acid. 
When  the  acid  solution  was  allowed  to  stand  the  hydrochloride 
separated  in  magnificent,  prismatic  crystals,  some  of  which 
measured  5  mm.  in  length.  The  prisms  showed  a  decided 
tendency  to  twin,  as  shown  in  Fig.  II.  The  salt  contained  i 
molecule  of  water  of  crystallization,  which  was  determined  by 
heating  at  i2o°-i3O°. 

0.0896  gram  substance  lost  0.0077  gram. 

Calculated  for 
C4H6ON4.2HC1.H2O.  Found. 

H2O  8.29  8.59 

Analysis  of  the  anhydrous  salt : 

Calculated  for 
C4H6ON4.2HC1.  Found. 

N  28.14  28.07 

The  nitrate,  C4H6ON4.2HNO3,  was  obtained  by  dissolving 
the  base  in  20  per  cent  nitric  acid  and  allowing  it  to  evaporate  in 
a  vacuum.  It  crystallized  in  beautiful  prisms,  which  were 
well  developed,  with  very  distinct  faces  (Fig.  III.).  They 
were  exceedingly  soluble  in  water.  The  salt  did  not  contain 
water  of  crystallization.  Analysis  : 

Calculated  for 
C4H6ON4.2HNO3.  Found. 

N  33-3  33-5 

The  sulplwte,  C4H6ON4.H2SO4,  was  easily  obtained  when  di- 
lute sulphuric  acid  was  added  to  an  aqueous  solution  of  the 
base.  It  was  very  difficultly  soluble  in  water  and  separated  in 
the  form  of  slender,  needle-like  prisms.  The  salt  showed  a 
tendency  to  crystallize  in  two  forms.  When  deposited  from 
water  it  usually  separated  in  clusters  of  radiating  needles. 
When  recrystallized  from  dilute  sulphuric  acid  solution  it 
formed  beautiful,  long,  slender  prisms  with  well-developed 
faces  (Fig.  IV.).  Neither  form  contains  water  of  crystalliza- 
tion. Both  forms  represent  the  same  salt.  The  salt  does  not 
decompose  below  300°. 


Fig.  I. -The  picrate  of  2,5-diamino-6-oXypyrimidine  crystallized  from  water.     Magni- 
fied 60  times. 


Fig  II.-The  hydrochlorideof  2,5-diamino-6-oxypyrimidine  crystallized  from  a  strong 
solution  of  hydrochloric  acid.    Magnified  60  times. 


\ 


X 


Fig.  III.— The  nitrate  of  2,5-diamino  6-oxypyrimidine  crystallized  from  a  strong  nitric 
acid  solution.     Magnified  60  times. 


Fig.  IV.— The  sulphate  of  2,5-diamino-6-oxypyrimidine  crystallized  from  dilute  sul- 
phuric acid.     Magnified  60  times. 


2 ,  s-Diamino-6-oxypyrimidine .  5  63 

Analysis  of  the  needles  and  prisms  of  the  salt  : 

Calculated  for  Found. 

C4H6ON4.H2SO4.  I.  II. 

N  25.00  24.81  24.74 

In  order  to  avoid  the  possibility  of  dissociation  in  aqueous 
solution,  solubility  determinations  of  the  sulphate  were  made 
in  normal  solutions  of  sulphuric  acid.  The  solubility  was  de- 
termined by  taking  exactly  10  cc.  of  the  acid  solution,  satura- 
ted at  25°,  and  determining  the  amount  of  nitrogen  present 
(Kjeldahl).  The  quantity  of  salt  dissolved  in  10  cc.  was  then 
calculated  from  the  weight  of  nitrogen  obtained.  One  hun- 
dred cc.  of  normal  sulphuric  acid  dissolved,  at  25°  : 

i.  ii. 

0.4928  gram.  0.4704  gram. 

While  the  2,5  diamino-6  oxypyrimidine  apparently  under- 
goes slow  decomposition  when  its  aqueous  solution  is  boiled, 
the  sulphate  appears  to  be  perfectly  stable  when  subjected  to 
the  same  treatment.  Some  of  the  sulphate  was  dissolved  in  20 
per  cent  sulphuric  acid  and  the  solution  boiled  for  about  one- 
half  hour.  The  sulphuric  acid  was  then  removed  by  digesting 
with  pulverized  barium  carbonate.  After  filtering  from 
barium  carbonate  and  barium  sulphate  the  filtrate  was  com- 
bined with  a  solution  of  picric  acid.  The  picrate  that  was  ob- 
tained agreed  in  all  its  properties  with  the  picrate  of  2,5-di- 
amino-6-oxypyrimidine.  Analysis : 

Calculated  for 
C4HeON4.C6H3O7N8.  Found. 

N  27.60  27.66 

Behavior  of  2,5-Diamino-6-oxypyrimidine  when  Heated  with 
Sulphuric  Acid  under  Pressure. — This  experiment  was  of 
especial  interest  since  Kutscher1  obtained  his  base  by  hydro- 
lyzing  nucleic  acid  with  sulphuric  acid,  at  a  high  temperature 
and  under  pressure.  One  gram  of  the  sulphuric  acid  salt  of 
the  pyrimidine  base  was  heated  in  a  sealed  tube,  with  10  cc.  of 
sulphuric  acid,  of  approximately  20  per  cent,  for  3  hours,  at 
I3o°-i4o°.  There  was  no  pressure  when  the  tube  was  opened 
and  no  apparent  decomposition  had  taken  place.  The  sul- 

1  Loc.  tit. 


564  Johnson  and  Johns. 

phuric  acid  was  removed  by  digesting  with  pulverized  barium 
carbonate  and,  after  filtering  from  barium  carbonate  and 
barium  sulphate,  the  filtrate  was  evaporated  over  a  free  flame 
to  about  50  cc.  Some  of  this  solution  was  taken  and  treated 
with  a  cold,  saturated  solution  of  picric  acid.  We  obtained  an 
immediate  precipitate  of  a  beautiful,  crystalline  picrate.  It 
was  extremely  insoluble  in  water.  It  separated  from  hot 
water  in  well-  developed  prisms,  which  arranged  themselves  in 
radiating  clusters.  The  picrate  had  all  the  properties  of  the 
picrate  of  2,5-diamino-6-oxypyrimidine.  Analysis  (Kjeldahl): 

Calculated  for 
C4H6ON4.CeH307N8.  Found. 

N  27.60  27.53 

The  remaining  portion  of  the  above  filtrate,  after  testing  for 
unaltered  base  with  picric  acid,  was  allowed  to  stand  for  2 
days,  when  a  small  amount  of  crystalline  material  separated. 
It  was  purified  by  recrystallizing  from  water,  from  which  it 
separated  in  clusters  of  microscopic  prisms.  When  heated  in  a 
capillary  tube  the  material  turned  brown,  but  did  not  decom- 
pose below  300°.  A  nitrogen  determination  agreed  very 
closely  with  the  calculated  for  aminouracil  or  its  isomer, 
2-amino-5,6-dioxypyrimidine.  The  low  result  obtained  was 
due  to  the  presence  of  a  minute  trace  of  inorganic  material 
(BaC08?). 

Calculated  for 

s.  Found. 


N  33.0  32.4 

In  order  to  distinguish  between  aminouracil  and  2-amino- 
5,6-dioxypyrimidine,  the  base  was  dissolved  in  hot  water  and 
treated  with  a  saturated  solution  of  picric  acid.  The  picrate 
separated  in  the  form  of  microscopic  prisms.  It  showed  no 
signs  of  decomposing  at  147°.  It  charred  at  24O°-25O°,  but 
did  not  effervesce  below  280°.  Aminouracil  decomposes  at 
247°  with  violent  effervescence.1 

Action  of  Ammonia  on  Bromisocytosine  or  2-Amino-$-brom-6- 
oxypyrimidine.  —  Three  grams  of  bromisocytosine2  were  heated 

1  Wheeler  and  Bristol  :  Loc.  cit. 

2  Wheeler  and  Johnson  :  Loc.  cit. 


2 ,  $-Diamino-6-oxypyrimidine.  565 

with  an  excess  of  aqueous  ammonia,  for  6  hours,  at  190°— 215°. 
When  the  tube  was  opened  the  solution  was  perfectly  clear 
and  no  resin  had  separated.  The  solution  gave  a  heavy  pre- 
cipitate of  silver  bromide  when  treated  with  nitric  acid  and  sil- 
ver nitrate.  The  ammoniacal  solution  was  evaporated  over  a 
free  flame  to  remove  the  excess  of  ammonia.  On  continued 
evaporation  the  solution  gradually  assumed  a  deep  wine  color 
and  a  slimy  deposit  slowly  formed  on  the  surface  of  the  liquid. 
After  the  excess  of  ammonia  was  removed  the  solution  was 
filtered  and  combined  with  a  solution  of  picric  acid,  which 
yielded  a  very  insoluble  picrate.  It  was  poorly  crystallized  and 
showed  no  definite  decomposition-point.  It  gave  no  test  for 
bromine.  A  nitrogen  determination  agreed  with  that  calcula- 
ted for  the  picrate  of  2,5-diamino-6-oxypyrimidine. 

Calculated  for 
C4H6NO4.C6H8O7N8.  Found. 

N  27.60  28.10 

Action  of  Ammonia  on  2-Ethylmercapto-5-amino-6-oxypyrimi- 
dine.1 — When  2-ethylmercapto-5-amino-6  oxypyrimidine  was 
heated  in  a  sealed  tube,  with  an  excess  of  concentrated  aqueous 
ammonia,  at  131°— 142°,  for  4  hours  it  was  recovered  unaltered. 
It  was  again  heated  for  3  hours,  at  i8o°-i9o°.  Under  these 
conditions  only  a  trace  of  mercaptan  was  detected  and  again 
unaltered  material  was  obtained.  Three  grams  of  the  mer- 
capto  derivative  were  then  heated  for  4  hours,  at  2oo°-2O5°, 
with  strong  alcoholic  ammonia.  When  the  tube  was  opened 
there  was  slight  pressure  and  a  strong  odor  of  mercaptan.  A 
small  amount  of  slimy,  insoluble  residue  had  also  separated. 
The  solution  was  filtered  and  evaporated  to  dryness.  We  ob- 
tained a  red-colored  oil,  which  showed  no  signs  of  solidifying. 
It  was  dissolved  in  water  and  boiled  with  animal  charcoal  to 
remove  the  color.  When  the  clarified  solution  was  treated 
with  picric  acid  we  obtained  a  picrate  which  was  difficultly 
soluble  in  water.  It  gave  no  test  for  sulphur  and  decomposed 
at  25o°-30o°,  according  to  the  rate  of  heating.  A  nitrogen 
determination  agreed  with  the  calculated  for  the  picrate  of 
2, 5-diamino-6-oxypyrimidine. 

1  Johnson  :  Loc.  cit. 


566  Johnson  and  Johns. 

Calculated  for 
C4H6ON4.C6H8O7N8.  Found. 

N  27.60  2?-?1 

Hydrochloric  Acid  Salt    of    2-Amino-5-benzoylamino-6-oxy- 
NH  -  CO 

I  I 

pyrimidine,  H2NC  CNHCOC6H6.  HCL—  An  aqueous  solu- 

II  II 
N  -  CH 

tion  of  guanidine  was  prepared  by  dissolving  25  grams  of 
guanidine  carbonate  in  water  and  then  adding  an  aqueous 
solution  containing  a  molecular  proportion  of  barium  hydrox- 
ide. The  barium  carbonate  was  filtered  off  and  to  the 
solution  was  added  50  grams  of  the  sodium  salt  of  ethyl 
formylhippurate.  The  solution  was  then  heated  on  the  steam- 
bath  for  1-2  hours.  The  clear  liquid  was  made  distinctly 
acid  with  sulphuric  acid  and  concentrated  to  about  one- 
half  its  volume.  Upon  cooling,  nothing  separated.  The  solu- 
tion was  now  treated  with  a  slight  excess  of  mercuric  chloride, 
when  a  white  mercury  salt  was  obtained.  This  was  washed 
with  water  and  decomposed  with  hydrogen  sulphide.  On 
evaporating  the  filtrate,  after  filtering  from  mercuric  sulphide 
and  cooling,  a  crystalline  product  was  obtained.  It  was  insol- 
uble in  alcohol,  but  crystallized  from  hot  water  in  microscopic 
needles.  It  contained  chlorine  and  decomposed  with  violent 
effervescence  at  about  275°.  We  did  not  obtain  a  sufficient 
amount  of  the  salt  to  isolate  the  free  base.  Analysis  (Kjel- 
dahl)  : 

Calculated  for 

Found. 


N  21.  01  21.04 

NHzizrCO 

I  I 
2-Benzalamino-6-oxy  pyrimidine,     C6H5CH  :  NC            CH.  — 

II  II 
N  --  CH 

Five  grams  of  isocytosine  were  heated  at  i6o°-i8o°,  for  3 
hours,  with  a  molecular  proportion  of  benzaldehyde.  Water 
was  given  off  and  a  yellow,  crystalline  cake  was  obtained.  It 


2 , s-Diamino-6-oxy pyrimidine.  5  67 

was  insoluble  in  water  and  alcohol.  It  showed  both  acid  and 
weak  basic  properties.  It  dissolved  in  ammonia  to  a  deep  red 
solution.  Its  salts  undergo  dissociation  in  aqueous  solution. 
Some  of  the  material  was  dissolved  in  20  per  cent  sulphuric 
acid  and  filtered  while  hot  into  cold  water.  The  base  was 
precipitated  at  once  as  a  yellow,  crystalline  solid.  After  wash- 
ing with  water  and  alcohol,  it  decomposed  at  238°-242°. 
Analysis  : 

Calculated  for 
CnH8ON3.  Found. 

N  21.10  21. II 

The  following  experiments  illustrate  the  remarkable  stability 
of  this  pyrimidine  towards  nitric  acid  :  Eight  and  one-half 
grams  of  the  crude  material  were  dissolved  in  a  mixture  of  20 
cc.  of  nitric  acid  (sp.  gr.  1.5)  and  15  cc.  of  concentrated  sul- 
phuric acid.  The  mixture  was  warmed  on  the  steam-bath  for 
3  hours  and  then  allowed  to  stand  for  24  hours  at  4O°-6o°. 
We  obtained  a  clear,  red  solution.  When  the  acid  solution 
was  poured  into  water  a  crystalline  product  separated  which 
was  identified  as  a  mixture  of  the  unaltered  benzal  derivative 
and  some  metanitrobenzaldehyde.  After  boiling  with  alcohol, 
to  remove  the  nitrobenzaldehyde,  the  benzalaminopyrimidine 
was  obtained,  melting  at  about  242°.  When  mixed  with  the 
pure  material  the  melting-point  was  not  altered.  When  the 
benzal  derivative  was  again  heated  with  a  mixture  of  nitric  acid 
(sp.  gr.  1.5)  and  concentrated  sulphuric  acid,  at  90°-! 00°,  no 
nitro-product  was  obtained  but  a  violent  oxidation  took  place 
and  the  pyrimidine  was  completely  decomposed. 

Action  of  Nitrous  Acid  on  Isocytosine. — Four  grams  of  isocyto- 
sine  were  dissolved  in  acetic  acid.  Into  this  solution  was  in- 
troduced solid  sodium  nitrite  and  the  liquid  allowed  to  stand 
over  night,  at  the  ordinary  temperature.  In  the  morning  a  crop 
of  microscopic  prisms  had  separated.  When  fused  on  platinum 
foil  they  left  no  inorganic  residue.  The  material  was  very 
soluble  in  cold  water.  It  turned  brown  at  about  280°,  but  did 
not  melt  at  300°.  A  nitrogen  determination  agreed -with  that 
calculated  for  an  acetic  acid  salt  of  isocytosine. 


568  Johnson  and  Johns. 

Calculated  for 
C6H9O3N3.  Found. 

N  24.56  24.26 

NEW  HAVEN,  CONN., 
June  7,  1905. 


I.— RESEARCHES  ON  PYRIMIDINS:  SOME  5-IODOPYRIMIDIN 
DERIVATIVES;  5-IODOCYTOSIN. 

PLATE  I. 

(Thirteenth  Paper.) 

BY  TREAT  B.  JOHNSON  AND  CARL  O.  JOHNS. 

(Contributions  from  the  Sheffield  Laboratory  of  Yale  University.} 

(Received  for  publication,  December  19,   1905.) 

The  object  of  the  work  described  in  this  paper  was  to  prepare 
some  5-iodopyrimidin  derivatives  and  investigate  their  behavior 
towards  ammonia  and  organic  bases.  It  was  considered  desir- 
able to  compare  the  reactivity  of  such  iodine  derivatives  with 
that  of  the  analogous  bromine  compounds.  In  the  course  of 
our  work  on  pyrimidins,  it  was  necessary  to  decide  whether 
5-iodopyrimidins  might  serve  for  syntheses  in  which  the  bromine 
derivatives  could  not  be  used. 

Several  iodine-substituted  pyrimidins  have  been  described  in 
the  literature,1  but  so  far  as  the  writer  is  aware  no  attempts  have 
hitherto  been  made  to  prepare  iodine  derivatives  by  direct 
iodation.  We  have  selected  for  our  investigation  three  pyrim- 
idin  derivatives,  in  which  the  4-  and  5 -positions  are  occu- 
pied by  hydrogen,  viz. :  2-ethylmercapto-6-oxypyrimidin,2  (I) ; 
2 , 6-dioxypyrimidin3  (Uracil,  II.) ;  and  2-oxy-6-amino-pyrimidin4 
(Cytosin,  III).  Wheeler  and  Bristol  have  shown  that  when 
such  pyrimidins  5  are  attacked  by  nitric  acid  or  bromine  it  is 
the  hydrogen  atom  occupying  the  5 -position  that  is  substituted. 
It  might  be  expected  that  they  would  be  attacked  by  iodine  in 
a  similar  manner  to  form  the  corresponding  5-iodopyrimidins. 

We  now  find  that  the  three  pyrimidins  selected  can  be  con- 

1  Gabriel  and  Colman,  Ber.  d.  deutsch.  chem.  Gesellsch.,  xxxii,  p.  1525, 
1899;  ibid.,  xxxii,    p.  2921,   1899;  Emery,  ibid.,  xxxiv,    p.   4178,  1901; 
Buttner,  ibid.,  xxxvi.  p.  2227,   1903. 

2  Wheeler  and  Merriam,  Amer.  Chem.   Jour.,  xxix,  p.  484,  1903. 

3  Wheeler  and  Merriam,  loc.  cit. 

4  Wheeler  and  Johnson,  ibid.,  xxix,  p.  492,  1903. 
*Ibid.,   xxxiii,  p.  437,  1905. 

305 


306  Researches  on  Pyrimidins 

verted  smoothly  into  5-iodopyrimidins  if  treated  with  iodine  in 
an  alkaline  solution. 

NH-CO  NH-CO  N   =  C.NH2 

II  II  II 

C2H5SC         CH  CO      CH  CO       CH 

II          II  I         II  I          II 

N   -  CH  NH-CH  NH-CH 
I                           II  III 

NH-CO  NH-CO  N    =  C.NH2 

II  II  II 

C2HSSC         CI  CO      CI  CO       CI 

II         II  I         II  I  II 

N  -  CH  NH-CH  NH  rCH 

IV  V  VI 

In  order  to  show  that  the  iodine  enters  the  pyrimidin  ring  in 
the  same  position  (5)  we  have  furthermore  prepared  5-iodo- 
cytosin  (VI)  from  2-ethylmercapto-5-iodo-6-oxypyrimidin  (IV). 
When  this  compound  was  warmed  with  phosphorus  oxy- 
chloride  it  was  converted  quantitatively  into  2-ethylmercapto- 
5-iodo-6-chlorpyrimidin  (VII). 

NH-CO  N=CC1 

II  II 

C2HSSC         CI  +  (POC13)  =C2HSSC       CI 

II          II  II       II 

N  -  CH  N-CH 

VII 

When  this  chlorpyrimidin  was  heated  with  alcoholic  ammonia 
it     reacted     quantitatively    to     form     2-ethylmercapto-5-iodo- 
6-aminopyrimidin    (VIII).      This    was    then    converted     into 
5-iodocytosin  (IX)    by   boiling   with   hydrochloric   acid.     This 
N=CC1  N=C.NH2 

II  II 

C2HSSC     CI  +  2NH3=C2HSSC     CI    +    NH4C1 
II       II  II       II 

N-CH  N-CH 

VIII 
N=C.NH2  N  =  C.NH1 

C2HSSC     CI  +  HC1  +    H:0=C2H5SH  +  CO     CI.HC2 

II       II  I         II 

N-CH  NH-CH 

IX 

synthesis  supports  the  assumption  that  the  iodine  in  these 
compounds  occupies  the  5-  and  not  the  4-position.  Buttner1 
has  shown  that  when  an  iodine  occupies  the  4-position  in  a 

1  Loc.  cit 


Treat  B.  Johnson  and  Carl  O.  Johns  307 

pyrimidin,  it  behaves  as  an  imide-chloride,  and  can  be  replaced 
by  an  amino-radical.  He  prepared  4,  6-diaminopyrimidin 
(XI)  by  heating  the  corresponding  4-iodo-6-aminopyrimidin  (X) 
with  alcoholic  ammonia. 

N=C.NH2  N=C.NH, 

II  II 

HC     CH   +   2NH3=HC     CH   +  NHJ 

II       II  II       II 

N-CI  N-C.NH2 

X  XI 

It  was   of   especial  interest  to   investigate   the   behavior  of 
5-iodocytosin    (VI)    towards    ammoniacal    solutions,    since    it 
offered  a  possibility  of  preparing  2-oxy-5,  6-diamino-pyrimidin 
(XII).      Furthermore  we  had  reason  to   expect   that    5-iodo- 
N   =  C.NH2  N    =  C.NH2 

II  II 

CO       CI  +  2NH3=CO       C.NH2+NHJ 
I  II  I  II 

NH  -  CH  NH  -  CH 

XII 

cytosin  (VI)  would  not  show  the  same  behavior  towards 
aqueous  and  alcoholic  ammonia.  Johnson  and  Johns1  have 
shown  that  such  ammoniacal  solutions  show  a  remarkable 
difference  in  their  reactivity.  We  now  find  that  this  iodo- 
pyrimidin  (VI)  can  be  heated  with  concentrated  aqueous  am- 
monia and  be  recovered  unaltered.  This  result  is  in  accord  with 
an  observation  made  by  Wheeler  and  Johnson2  in  their  exam- 
ination of  the  properties  of  the  corresponding  5-bromcytosin. 
On  the  other  hand  when  5-iodocytosin  was  heated  with  strong 
alcoholic  ammonia  under  the  same  conditions  with  respect  to 
temperature  and  time  of  heating,  it  was  reduced  practically 
quantitatively  to  cytosin  (XIII). 

N    =    C.NH2  N    =   C.NH2 

II  II 

CO        CI  + (Alcoholic  Ammonia,  1 70°- i8o°C.)=  CO        CH 

II  I  II 

NH -CH  NH-CH 

XIII 

We  now  find  that  2-ethylmercapto-5-iodo-6-oxypyrimidin 
(IV)  and  5-iodouracil  (V)  likewise  show  a  remarkable  difference 
in  behavior  towards  aqueous  and  alcoholic  ammonia  solutions. 
The  mercaptopyrimidin  (IV)  can  be  heated  with  alcoholic  atn- 

1  Ibid.,  xxxiv,  p.  175,  1905. 

2  Ibid.,  xxxi,  p.  591,  1904. 


308  Researches  on  Pyrimidins 

monia  and  recovered  unaltered.  On  the  other  hand  when  heated 
with  concentrated  aqueous  ammonia  at  the  same  temperature 
mercaptan  was  evolved  and  it  was  converted  into  2-amino-6-oxy- 
pyrimidin  (Isocytosin,  XIV).  5-Iodouracil  reacted  in  a  reverse 
manner.  When  heated  with  aqueous  ammonia  it  was  recovered 
unaltered.  On  the  other  hand  it  was  converted  by  alcoholic 
ammonia  into  uracil  (XV).  The  action  of  alcoholic  or  aqueous 
NH-CO  NH-CO 

II  II 

C2HSSC     CI  +  (Aqueous  Ammonia,  1 560-i63°C.)  =  NH2.C     CH+C2HSSH 
II       II  II       II 

N-CH  N-CH 

XIV 

NH-CO  NH-CO 

II  II 

CO      CI  +  (Alcholic  Ammonia,  i7o°-i8o°  C.)  =  CO     CH 

I  II  I  II 

NH-CH  NH-CH 

XV 

ammonia  on  2-ethylmercapto-5-brom-6-oxypyrimidin1  at  tem- 
peratures between  140°  and  200°  C.  does  not  give  smooth  results. 
Merriam2  has  shown  that  5-bromuracil  is  converted  smoothly 
into  5-amino-uracil  when  heated  with  aqueous  ammonia. 

We  have  observed  that  this  replacement  of  iodine  by  a  hydro- 
gen atom  can  take  place  in  the  presence  of  aniline  as  well 
as  ammoniacal  solutions.  When  2-ethylmercapto-5-iodo-6- 
oxypyrimidin  (IV)  was  heated  with  aniline  at  100°  C.,  mercaptan 
was  evolved  and  2-anilino-6-oxypyrimidin  (XVI)  was  formed. 
NH-CO  NH-CO 

II  II 

C2H5SC        CI  +  C6HSNH2  =C2HSSH  +C6H5NH.C        CH 
II  II  II  II 

N-CH  N-CH 

XVI 

The  same  amlmo-pyrimidin  was  obtained  when  2-ethylmercapto- 
6-oxypyrimidin  (I)  was  heated  with  aniline  at  100°  C.  This 
abnormal  result  again  illustrates  the  difference  in  behavior  be- 
tween 5-iodopyrirnidins  and  their  bromine  analogues.  The 
corresponding  2-ethylmercapto-5-brom-6-oxypyrimidin  reacts 
quantitatively  with  aniline  at  100°  C.  to  form  2-anilino-5-brom- 
6-oxypyrimidin,  3 

»  Wheeler  and  Johnson,  loc.  cit. 
2  Amer.  Chem.  Jour.,  xxxi,  p.  603,  1904. 
'»  Wheeler  and  Bristol,  ibid.,  xxxiii,  p.  444,  1905. 


Treat  B.  Johnson  and  Carl  O.  Johns  309 

NH-CO  NH-CO 

II  II 

C2HSSC        CBr  +  C6H5NH2=C2H5SH+C6HsNH.C        CBr 
N"  -  CH  N  -  CH 

It  is  a  remarkable  fact  that  the  reduction  of  2-ethylmercapto-5- 
iodo-6-oxypyrimidin  to  2-ethylmercapto-6-oxypyrimidin  should 
take  place  at  a  much  lower  temperature  with  aniline  than  with 
ammonia.  In  our  experiments  with  iodocytosin  we  did  not 
observe  the  formation  of  cytosin  when  it  was  heated  with  ani- 
line. It  was  recovered  unaltered  after  heating  with  aniline  from 
190°  to  200°  C. 

We  are  not  inclined  to  consider  these  abnormal  replacements 
of  iodine  by  hydrogen  as  exceptional  cases  of  reduction.  It 
seems  probable  to  the  writer  that  the  mechanism  of  these  in- 
teresting reactions  is  analogous  to  that  when  diethylbrom- 
nitromalonate  is  treated  with  amines.  This  ester  was  investigated 
by  Willstatter  and  Hottenroth  *  in  their  attempts  to  synthesize 
Drechsel's  diamino-acetic  acid.2  They  observed  that  the 
bromine  atom  in  this  ester  was  extremely  loosely  bound,  and  it 
was  reduced  to  diethylnitromalonate  when  treated  with  am- 
monia or  fatty  amines.  They  showed  that  it  reacted  with 
dimethylamine  according  to  the  following  equation: 
Br  COOC,H5 

^>C/  +2NH(CH3)2  =Br  N(CH3)2  + 

NO2          COOC2H5 

COOC2HS 

NO2CH/  NH(CH3) 

COOC2HS 

The  ease  with  which  the  iodine  in  2-ethylmercapto-5-iodo-6- 
oxypyrimidin  (IV)  could  be  replaced  by  hydrogen  in  the  pres- 
ence of  amines  suggested  that  this  iodopyrimidin,  under  certain 
conditions,  might  be  used  for  syntheses  in  reactions  involving 
double  decomposition.  We  now  find  that  under  the  conditions 
employed  in  our  experiments  the  iodine  was  very  firmly  bound  and 
could  not  be  replaced.  For  example:  It  could  be  heated  with 
the  potassium  salt  of  phthalimid  in  alcohol,  or  with  the  sodium 
salt  of  urethane  in  benzene  at  160°  C.  and  be  recovered  unaltered. 
In  these  experiments  it  shows  the  stability  of  the  corresponding 
i  lJ3er.  d.  deutsch.  chem.  Gescellsch.,  xxxvii,  p.  1775,  1904. 

2  Beilstein,  Handbuch,  i,  p.  1194. 


3io  Researches  on  Pyrimidins 

bromine  derivative —  2-ethylmercapto-5-brom-6-oxypyrimidin. 
This  compound  and  also  2-ethylmercapto-5-brom-6-amino-pyr- 
imidin  *  could  be  heated  with  the  potassium  salt  of  phthalimid 
at  200°  C.  without  any  evidence  of  the  formation  of  potassium 
bromide. 

EXPERIMENTAL    PART. 


NH-CO 

I          I 
2-Eihylmercapto-5-iodo-6-oxypyrimidin,       C,H5SC       CI       (by 

N   -  CH 

Dr.  J.  G.  Statiropulos) . — Ten  grams  of  2-ethylmercapto- 
6-oxypyrimidin  ,2  were  dissolved  in  50  c.c.  of  water  containing 
3  grams  of  sodium  hydroxide.  To  this  solution  was  then  slowly 
added  1 7  grams  of  pulverized  iodine.  After  all  the  iodine  had 
been  added  the  solution  was  warmed  on  the  steambath  until 
the  free  iodine  dissolved.  The  iodopyrimidin  separated  from  the 
hot  solution.  After  acidifying  with  acetic  acid  the  solution 
was  filtered  and  the  pyrimidin  purified  by  crystallization  from 
alcohol.  It  deposited  in  slender  prisms,  arranged  in  crosses,  and 
melted  at  i96°C.  to  a  clear  oil.  It  was  insoluble  in  water,  and 
readily  soluble  in  benzene.  The  yield  was  practically  quanti- 
tative. Analysis: 

For  C6H7ON2SI— 

Calculated:  N=9-93  per  cent. 
Found:  N.  =  10.02  per  cent. 

NH-CO 

2,  6 -Dioxy- 5 -iodopyrimidin    (^-iodouracil) ,  CO      CI     (by 

I         II 
NH-CH 

Dr.  J.  G.  Statiropulos). — This  compound  was  easily  obtained 
when  uracil  was  dissolved  in  alkali  and  treated  with  iodine  as  in 
the  preparation  of  the  above  2-ethylmercapto-5-iodo-6-oxypyr- 
imidin.  It  crystallized  from  hot  water  in  glistening  scales,  and 
decomposed  at  272°  C.  It  was  soluble  in  hot  alcohol.  Analysis: 

1  Wheeler  and  Johnson,  loc.  cit. 

2  Wheeler  and  Merriam,  loc.  cit. 


Treat  B.  Johnson  and  Carl  O.  Johns  311 

For  C4H3O2NJ— 

Calculated:  N  =  11.86  per  cent. 
Found:  N  =  n.77  per  cent. 

N  =  C.  NH2 

^-Iodocytosin,  CO      CI.— Six  and  three-tenths  grams 

NH-CH 

of  synthetical  cytosin1  were  dissolved  in  about  50  c.c.  of  water 
containing  3.3  grams  of  potassium  hydroxide.  To  this  solu- 
tion were  slowly  added,  with  frequent  shaking,  14.5  grams 
of  finely  pulverized  iodine.  The  reaction  was  smooth  and  the 
iodocytosin  began  to  separate  immediately.  After  all  the  iodine 
had  been  added  the  solution  was  warmed  on  the  steambath  for 
a  few  minutes  to  complete  the  reaction.  After  neutralizing  the 
free  alkali  with  acetic  acid  the  base  was  filtered  off  and  re- 
crystallized  from  boiling  water.  It  separated  on  cooling  in 
characteristic,  branched  crystals  (Figure  i),  which  decomposed 
between  225°  and  245°  C.  without  effervescence,  giving  off 
iodine  vapors. 

It  was  practically  insoluble  in  alcohol  and  benzene.  The 
yield  was  quantitative.  Analysis  (Kjeldahl): 

0.1188  gm.  of  substance  gave  0.0210  gm.  of  nitrogen  =  15  c.c.  of  TIT  HC1. 
For  C4H4ON3I— 

Calculated:  N  =  i7-72  per  cent. 
Found:  1^  =  17.67  per  cent. 

Solubility  of  iodocytosin  in  water :  One  liter  of  water  at 
25°  C.  dissolved  (i)  0.936  gram,  (2)  0.988  gram. 

Iodocytosin  is  very  stable  in  the  presence  of  boiling  hydro- 
chloric acid.  One  gram  of  the  base  was  boiled  with  concentrated 
hydrochloric  acid  for  two  hours.  The  acid  solution  was  then 
evaporated  to  dryness  and  the  residue  treated  with  a  little  dilute 
ammonia.  We  obtained  the  unaltered  base  which  decomposed 
at  from  220°  to  235°C.  Analysis  (Kjeldahl) : 

0.12 10  gm.  of  substance  gave    0.02 142  gm.  of  nitrogen  =  15.  3  c.c.  ^  HCI. 
For  C4H4ON3I— 

Calculated:  N  =  i7.72  per  cent. 
Found:  N  =17.70  per  cent. 

Pier  ate  of  iodocytosin:  The  picrate  crystallized  from  hot 
water  in  long  needles.  It  had  no  definite  melting  point  but 

1  Wheeler  and  Johnson,  loc.  cit. 


312  Researches  on  Pyrimidins 

decomposed  with  effervescence  at  from  247°  to  257°C.  according 
to  the  rate  of  heating.     Analysis  (Kjeldahl): 

0.1705  gm.  of  substance  gave  o. 03066  grm.  of  nitrogen  =  2 1.9  c.c.  T^  HC1 
For  C4H4ON3I.C6H3O7N3— 

Calculated:  N  =  18.02  p^r  cent. 
Found:  N  =  17.98  per  cent. 

Acetic  acid  salt  of  iodocytosin:  This  salt  is  of  special  interest 
on  account  of  its  dissociation  in  a  hot  solution  of  acetic  acid. 
Some  iodocytosin  was  dissolved  in  hot  acetic  acid  and  the  solution 
divided  into  two  equal  parts.  The  first  part  was  then  cooled 
quickly,  when  the  unaltered  base  immediately  separated  in  the 
form  of  irregular  prisms.  Analysis  (Kjeldahl) : 

0.1253  S00"  of  substance  gave  0.02198  gm.  of  nitrogen  =  15.70.0.  T^  HC1. 
For  C4H4ON3I— 

Calculated:  N  =  i7-72  per  cent. 
Found:  N  =  i7.54  p^r  cent. 

The  second  part  was  allowed  to  stand  for  several  hours.  The 
unaltered  base  separated  at  first  in  distorted  prisms.  On  stand- 
ing these  prisms  slowly  assumed  a  new  form  and  were  trans- 
formed into  large  well  developed  prisms  with  distinct  faces 
(Figure  2).  They  became  opaque  at  about  no°C.,and  decom- 
posed at  from  220°  to  2 40°  C.  according  to  the  rate  of  heating. 
A  nitrogen  determination  agreed  with  the  calculated  percentage 
in  the  acetic  acid  salt  (Kjeldahl): 

o.i32ogm.of  substance  gave  0.0189  gm.  of  nitrogen  =  13. 5  c.c.^HCl 
0.1029  gm.  of  substance  gave  0.01456  gm.  of  nitrogen  =  10.4.  c.C'nrHCl. 
For  C6H8O3N3I— 

Calculated:  N  =  i4.T4  per  cent. 

Found:  N  =  (i)  14.31;  (2)  14.15  per  cent. 

In  order  to  decide  whether  the  salt  would  dissociate  again,  it 
was  dissolved  in  hot  acetic  acid  and  the  solution  cooled.  The 
base  was  again  obtained  in  the  form  of  irregular  prisms.  Analysis 
(Kjeldahl): 

0.0811  gm.  of  substance  gave    0.01428  gm.of  nitrogen  =10. 2  c.c.  T^ 
For  C4H4ONJ— 

Calculated:  N  =  i7-72  per  cent 
,  ,     Found:  N  =  i7.6o  per  cent. 


Treat  B.  Johnson  and  Carl  O.  Johns  313 

N=CC1 

2-Ethylmercapto-5-iodo-6-chlorpyrimidin,     C2HSSC    CI 

!!       II 
N-CH 

This  compound  was  prepared  by  warming  on  the  steambath 
20  grams  of  2-ethylmercapto-5-iodo-6-oxypyrimidin  with  50  c.c. 
of  phosphorus  oxy chloride.  After  the  evolution  of  hydrochloric 
acid  ceased  the  excess  of  phosphorus  oxychloride  was  removed 
by  heating  at  100°  C.  under  a  pressure  of  50  millimeters  of  mer- 
cury. We  obtained  a  thick,  brown  varnish  which  immediately 
solidified  when  triturated  with  ice  water.  This  contained 
iodine  and  melted  at  68°  C.  to  a  turbid  oil.  It  was  purified  by 
crystallizing  from  petroleum  ether.  It  deposited  in  large  prisms 
and  melted  at  69°  C.  to  a  clear  oil.  The  yield  was  20  grams, 
or  95  per  cent,  of  the  theoretical.  Analysis  (Kjeldahl): 

0.2050  gm.  of  substance  gave  0.01918  gm.  of  nitrogen  =  i3.7  c.c.  y^HCl. 
For  C6H6N2SC1I— 

Calculated:  N=9-32  p«.r  cent. 
Found:  N=9-35  per  cent. 

N=C.NH2 

2-Ethylmercapto-5-iodo-6-aminopyrimidin,  C2H5SC    CI 

II       II 
N-CH 

This  compound  was  obtained  when  10  grams  of  2-ethylmercapto- 
5-iodo-6-chlorpyrimidin  were  heated  with  alcoholic  ammonia  for 
three  hours  at  i28°-i3o°  C.  When  the  tube  was  examined  the 
base  had  crystallized  from  the  alcoholic  solution  in  long,  slender 
prisms.  The  crude  material  melted  at  126°  C.  When  allowed 
to  crystallize  slowly  from  alcohol  it  deposited  in  slender  prisms 
that  arranged  themselves  in  clusters  radiating  from  a  common 
center.  It  melted  at  127°  C.  The  yield  was  quantitative. 
Analysis  (Kjeldahl): 

0.1368  gm.  of  substance  gave  0.02044  gm.  of  nitrogen  =14. 6  c.c.  T^  HC1. 
For  C6H8N3SI— 

Calculated:  N  =  i4-94  per  cent. 
Found:  N  =  i4-94  per  cent. 

When  5  grams  of  this  amino-pyrimidin  were  boiled  with  con- 
centrated hydrochloric  acid  for  one  hour  mercaptan  was  evolved 


314  Researches  on  Pyrimidins 

and  it  was  converted  practically  quantitatively  into  5-iodo- 
cytosin.  Analysis  (Kjeldahl): 

0.1386  gm.  of  substance  gave  0.02422  gm.  of  nitrogen  =  17.3  c.c.  T^  HC1. 
For  C4H4ON3I— 

Calculated:  N  =  i7.72  per  cent. 
Found:  N  =  i7-47  per  cent. 

N=C.NHC6H5 

2-Ethylmercapto-^-iodo-6-anilino-pyrimidin,  C2HS  SC  —  CI 

II      II 
N-CH 

was  obtained  by  warming  a  benzene  solution  of  2  grams  of 
2-ethylmercapto-5-iodo-6-chlorpyrimidin  and  1.4  grams  of  aniline. 
After  evaporating  the  excess  of  benzene  and  washing  with  water 
to  dissolve  aniline  hydro  chloride,  the  base  was  obtained  as  an 
oil  which  would  not  solidify.  It  was  purified  by  converting  it, 
into  its  sulphuric  acid  salt.  This  crystallized  from  alcohol,  which 
contained  sulphuric  acid,  in  well  developed  prisms.  The  sulphate 
had  no  definite  melting  point  but  decomposed  above  200°  C.  A 
nitrogen  determination  (Kjeldahl)  agreed  with  the  calculated 
value  for  a  normal  sulphate: 

0.0923  gm.  of  substance  gave  0.00938  gm.  of  nitrogen  =  6. 7  c.c.    ™   HC1. 
For  (C12H12N3SI)2H2S04— 

Calculated:  N  =  io.34  per  cent. 
Found:  N  =  10.17  Per  cent. 

NH-CO 

2-Anilino-6-oxypyrimidin,  C6HSNH.C       CH.— This    compound 

N-CH 

was  prepared  by  warming  on  the  steambath  2-ethylmer- 
capto-6-oxypyrimidin  with  the  calculated  quantity  of  aniline. 
It  was  also  formed  when  an  alcoholic  solution  of  the  mercapto- 
pyrimidin  and  aniline  were  digested  for  several  hours.  It  was 
moderately  soluble  in  alcohol,  and  insoluble  in  benzene  and 
water.  It  was  purified  for  analysis  by  crystallization  from 
alcohol.  It  deposited  in  well  developed  plates  and  melted  at 
23o°-23i°  C.  to  a  yellow  oil.  Analysis: 

For  C10H9ON3— 

Calculated:  N  =  22.46  per  cent. 
Found:  N  =  22.54  per  cent. 

Action  of  Aniline  on  2-Ethylmercapto-^-iodo-6-oxypyrimidin. — 
Fifteen  grams  of  the  iodopyrimidin  were  heated  on  the  steambath 


Treat  B.  Johnson  and  Carl  O.  Johns  315 

with  2  5  grams  of  aniline  for  six  hours.  It  dissolved  in  the  warm 
aniline  to  give  a  clear  solution  which  gradually  assumed  a  dark 
blue  color.  After  the  evolution  of  mercaptan  ceased,  the  excess 
of  aniline  was  removed  by  distillation  with  steam.  We  obtained 
a  dark  crystalline  product  that  was  insoluble  in  water.  It  was 
washed  with  cold  alcohol  to  remove  the  coloring  matter  and  puri- 
fied by  repeated  crystallizations  from  alcohol  and  acetic  acid. 
It  failed  to  respond  to  tests  for  iodine  and  sulphur.  It  melted 
at  23o°-23i°  C.  to  a  yellow  oil.  It  agreed  in  all  its  properties 
with  2 -anilino-6-oxy pyrimidin  (M.  P.  23o°-23i°  C.).  A  mixture 
of  the  two  compounds  melted  sharply  at  23o°-23i°  C.  Analyses 
for  carbon,  hydrogen,  and  nitrogen  gave  the  following  results: 

0.0845  S01-  °f  substance  gave  16.7  c.c.  nitrogen  gas  at  20°  C.  and  768 
mm. 

0.2491  gm.  of  substance  gave  o.iiQ3gm.  of  H2O  and  0.5881  gm.  of  CO2. 

Calculated  for  Ci0H9ON3 —  Found— 

C           64.2  percent  64.4  percent 

H            4.8     "     "  5.3     "      " 

N          22.46  "      "  22.8     "      " 

Action  of  Aniline  on  2-Ethylmercapto-^-iodo-6-aminopyrimidin. 
— This  pyrimidin  was  recovered  unaltered  after  heating  with 
aniline  for  nine  hours  at  ioo°C.  It  melted  at  i27°C.  and  when 
mixed  with  the  original  material  the  melting  point  was  not 
lowered. 

Action  of  Aniline  on  $-Iodocytosin. — This  base  was  recovered 
unaltered  after  heating  with  aniline,  in  benzene,  for  one  hour  at 
i5o°-i6o°C.  The  temperature  was  then  raised  to  i90°-i93°C., 
and  maintained  for  two  hours.  When  the  tube  was  examined 
there  was  no  evidence  that  any  reaction  had  taken  place.  The 
iodocytosin  was  again  recovered  unaltered. 

Action  of  Aqueous  Ammonia  on  2-Ethylmercapto-$-iodo-6-oxy- 
pyrimidin. — Five  grams  of  the  pyrimidin  were  heated  with 
concentrated  aqueous  ammonia  for  three  hours  at  156°  to  163°  C. 
When  the  tube  was  examined  the  solution  had  assumed  a  red 
color  and  drops  of  mercaptan  were  floating  on  the  surface  of  the 
liquid.  The  solution  gave  a  strong  test  for  iodine.  The  am- 
moniacal  solution  was  evaporated  to  dry  ness.  We  obtained  a 
crystalline  residue  that  was  soluble  in  water  except  a  small 
amount  of  white  crystalline  material.  This  was  identified  as 


316  Researches  on  Pyrimidins 

the  unaltered  2-ethylmercapto-5-iodo-6-oxypyrimidin.  It  melted 
at  196°  C.  and  gave  a  strong  test  for  iodine.  The  aqueous  fil- 
trate was  concentrated  on  the  steambath  and  combined  with  a 
strong  solution  of  picric  acid.  We  obtained  a  beautiful  yellow 
picrate  that  crystallized  from  hot  water  in  prisms.  It  had  no 
definite  melting  point  but  decomposed  above  26o°C.  and  effer- 
vesced violently  at  about  285°C.  It  did  not  contain  water  of 
crystallization.  It  contained  neither  iodine  nor  sulphur.  A 
nitrogen  determination  agreed  with  the  calculated  value  for 
2-amino-6-oxypyrimidin  (XIV)  (Isocytosin) .  Analysis: 

0.1229  gm.  of  substance  gave  0.03052  gm.of  nitrogen  =  2 1.8  c.c.T^  HC1. 
For  C4H5ON3.C6H3O7N3— 

Calculated :   N  =  24 .  70  per  cent. 
Found:  N  =  24.83  per  cent. 

Action  of  Alcoholic  Ammonia  on  2-Ethylmercapto-$-iodo-6-oxy- 
pyrimidin. — After  heating  the  pyrimidin  with  alcoholic  ammonia 
for  six  hours  at  141°  to  148°  C.  it  was  recovered  unaltered.  It 
was  then  heated  for  six  hours  at  150°  to  i55°C.  Under  these 
conditions  only  a  trace  of  mercaptan  was  detected.  The  con- 
tents of  the  tube  were  evaporated  to  dry  ness.  We  obtained  a 
crystalline  residue.  This  was  insoluble  in  water  and  after  one 
crystallization  from  alcohol  it  melted  at  195°  C.  It  contained 
both  sulphur  and  iodine.  When  mixed  with  the  original  2- 
ethylmercapto-5-iodo-6-oxypyrimidin  the  melting  point  was  not 
altered.  We  did  not  detect  the  presence  of  any  isocytosin. 

Action  of  Alcoholic  Ammonia  on  j-Iodocytosin. — Five  grams  of 
iodocytosin  were  heated  with  strong  alcoholic  ammonia  for  six 
hours  at  170°  to  180°  C.  When  the  tube  was  opened  considerable 
decomposition  had  taken  place,  and  a  well  crystallized  product 
was  suspended  in  the  alcohol.  It  crystallized  from  hot  water 
in  plates.  It  did  not  melt  below  300°  C.  and  contained  no  iodine. 
It  contained  one  molecule  of  water  of  crystallization  and  agreed 
in  all  its  properties  with  cytosin.  Analysis: 

0.2711  gm.of  substance  lost  0.0372  gm.  of  H2O  at  no°-i2o°C. 
For  C4H5ON3.H2O— 

Calculated:   H2O  =  i3.95  percent. 
Found:  H2O  =  i3.72  per  cent. 

o  0909  gm.  of  anhydrous  base  gave  0.0343  gm.  of  nitrogen  =  24. 5  c.c. 
TNHC1. 


Treat  B.  Johnson  and  Carl  O.  Johns  317 

For  C4HSON3— 

Calculated :   N  =  3  7 . 84  per  cent. 
Found:  N  =  37-73  per  cent. 

Action  of  Aqueous  and  Alcoholic  Ammonia  on  j-Iodouracil. — 
When  iodouracil  was  heated  with  concentrated  aqueous  am- 
monia at  i7o°-i8o°C.  for  four  hours  it  was  recovered  unaltered. 
Some  of  the  pyrimidin  was  then  heated  with  strong  alcoholic 
ammonia  under  the  same  conditions.  When  the  tube  was  ex- 
amined slight  decomposition  had  taken  place  and  a  colorless 
compound  was  suspended  in  the  alcohol.  It  crystallized  from 
hot  water  in  balls  of  microscopic  prisms  and  did  not  melt  below 
3oo°C.  More  of  the  same  material  was  obtained  when  the  al- 
coholic solution  was  concentrated.  It  did  not  contain  iodine 
and  was  identified  as  uracil.  The  yield  was  practically  quanti- 
tative. We  did  not  detect  the  presence  of  any  amino-uracil. 
Analysis  (Kjeldahl): 

0.1192  gm,  of  substance  gave  0.02982  gm.  of  nitrogen  =  21. 3  c.c.  ^ 
0.0757  SP*-  °f  substance  gave  0.0189  g111-  °f  nitrogen  =  13. 5  c.c.  T^ 
For  C4H4(XN2— 

Calculated :   N  =  25  .  oo  per  cent. 

Found:  N=  (i)  25.01;  (2)  24.96  per  cent. 

a-Cyanbutyrylurea,  CH3.  CH2.  CH  (CN).  CO.  NH.  CO.  NH2.— 
This  compound  was  obtained  by  condensing  a-cyanbutyric  acid 
with  urea.  We  proceeded  according  to  the  directions  given  by 
Traube1  for  the  preparation  of  cyanacetylurea  from  cyanacetic 
acid  and  urea.  It  crystallized  from  water  in  arborescent  crystals 
and  melted  at  i8i°C.  with  slight  effervescence.  Analysis: 

For     C6H902N3— 

Calculated :   N  =  2  7 .  i  per  cent. 
Found :  N  =  2  7 . 5  per  cent. 

N=C.NH2 
2,  4-Dioxy-5-ethyl-6-aminopyrimidin,  \       \ 

CO  CHC2  H5.-  a-Cyanbu- 

NH-CO 

tyrylurea  dissolved  in  33  per  cent,  sodium  hydroxide  solu- 
tion with  'absorption  of  heat.  Fourteen  grams  of  the  urea 
were  dissolved  in  42  grams  of  the  alkali  solution  and  allowed  to 
stand  for  several  hours  at  ordinary  temperature.  The  solution 
was  then  neutralized  with  hydrochloric  acid.  We  obtained  a 
1  Ber.  d.  deutsch.  chem.  Gesellsch.,  xxxiii,  p.  1371,  1900. 


318  Researches  on  Pyrimidins 

beautiful  crystalline  product  that  decomposed  at 
with  violent  effervescence.  It  crystallized  from  hot  water  in 
needle-like  prisms  and  decomposed  at  339°  C.  with  effervescence 
(using  an  Anschutz  thermometer).  It  was  soluble  in  hydro- 
chloric acid,  and  was  reprecipitated  unaltered  with  ammonia. 
Analysis : 

For  C0H902N3— 

Calculated :   N  =  2  7 .  i  per  cent. 

Found:  N  =  26.9  per  cent. 

DESCRIPTION  OF  PLATE  I. 

Figure  i.   5-Iodocytosin,  crystallized  from  hot  water.     Magnified  60 
times. 

Figure  2.     The  acetic  acid  salt  of  5-iodocytosin.     Magnified  60  times. 


THE  JOURNAL  OF  BIOLOGICAL  CHEMISTRY.     VOL.  I.     PLATE  I. 


FIGURE    I. 


FIGURE   2. 


II.     RESEARCHES  ON  PYRIMIDINS:    ON  METHODS  OF  SYN- 
THESIZING ISOBARBITURIC  ACID,  AND  5-OXY- 
CYTOSIN. 

(Fourteenth  Paper.) 

BY    TREAT  B.  JOHNSON  AND  ELMER  V.  McCOLLUM. 
(From  the  Sheffield  Laboratory  of  Yale  University.} 
(Received  for  publication,  January  2,  1906.) 

In  this  paper  we  describe  a  new  synthesis  of  isobarbituric  acid, 
I.  In  the  course  of  the  work  we  have  also  prepared  several  new 
derivatives  of  this  acid  and  of  cytosin,  II,  which  are  of  especial 

interest. 

NH— CO  N   =   C.NH2 

II  II 

CO      COH  CO        CH 

I         II  I          II 

NH-CH  NH-CH 

I  II 

Wislicenus  and  Scheidt1  have  shown  that  diethyloxalate 
condenses  with  the  ethyl  ester  of  ethylglycollic  acid,  in  presence 
of  sodium  ethylate,  to  form  diethyloxalethylgly collate,  III. 

COOC2HS 

+  C2H5O.  CH2.  COOC2HS- 
COOC2H5  C2H5OH  +  C2H5OOC.  CO.CH(OC2H5).COOC2HS. 

Ill 

It  was  also  observed  by  Conrad 2  that  diethylglycollate  undergoes 
an  inner  condensation,  in  benzene,  in  the  presence  of  metallic 
sodium  to  form  the  sodium  salt  of  ethyl  a,  >/-diethoxyacetoace- 
tate3,IV. 

2C2H5O.CH2.COOC2Hs+Na    =    C2H5O.CH2.CO.C.Na.(OC2H5).COOC2Hs 

+  C2HSOH. 
IV 

It  might  be  expected  that  ethylformate  would  also   condense. 

1  Ber.  d.  deutsck.  chem.  Gesellsch.,  xxiv,  p.  432,  1891. 

2  Ibid.,  xi,  p.  58,  1878. 

3  Ann.  d.  Chem.  (Liebig),  cclxix,  p.  28,  1892. 

437 


438  Researches  on  Pyrimidins 

with  diethylglycollate  in  the  presence  of  metallic  sodium  to 
form  the  sodium  salt  of  ethyl-tf-ethoxy-0-oxyacrylate,1  V.  We 
find  that  this  condensation  takes  place  in  the  normal  manner 
according  to  the  following  equation: 

C2HSO.CH2.COOC2H5  +H.COOC2H5  +Na  = 

C2HsOH  +  C2HsO.C:(CHONa)COOC2H5 
V 

When  this  sodium  salt,  V.,  was  dissolved  in  water  with  the 
calculated   quantity   of  pseudoethylthiourea   they   reacted    to 
form  2-ethylmercapto-5-ethoxy-6-oxypyrimidin,  VI.,  as  follows  : 
NH2         COOC2H5  NH— CO 

C2HSSC        +     COC2HS    =  C2H$SC         COC2HS +C2HsOH  +  NaOH 

II  II  II          II 

NH  CHONa  N CH 

VI 

This  mercaptopyrimidin,  VI.,  was  converted  practically 
quantitatively  into  isobarbituric  acid,  I.,  when  heated  with 
hydrochloric  acid.  This  change  involves  two  distinct  reactions, 
as  follows:  The  2-ethylmercapto-5-ethoxy-6-oxypyrimidin,  VI., 
is  first  converted  into  2,6-dioxy-5-ethoxypyrimidin,  VII.,  with 
evolution  of  ethylmercaptan.  This  intermediate  ethoxy- 
NH— CO  NH— CO 

C2H5SC        COC2HS+H2O  =  CO      COC2HS     +     C2H5SH 


N CH  NH— CH 

VI  VII 

pyrimidin,   VII.,   then  reacts  with  hydrochloric  acid  to  give 
isobarbituric  acid,  I.,  with  formation  of  ethylchloride. 
NH— CO  NH— CO 

CO       COC2HS+HC1=    CO       COH+C2H5C1 

NH— CH  NH— CH 

VII  I 

The  only  method,  given  in  the  literature,  for  preparing  isobar- 
bituric acid  is  that  described  by  Behrend.2  He  prepared  it  by 
reducing  nitrouracil,  VIII.,  with  tin  and  hydrochloric  acid. 

»We  find  that  ethylformate  condenses  with  ethylphenoxyacetate — 
C6H5O.CH2.COOC2HS — to  give  a  quantitative  yield  of  the  sodium 
salt  of  ethyl -a- phenoxy-/?-oxyacrylate— C6H5O.C:(CHONa).COOC2Hb. 
We  shall  condense  ethylformate  with  other  glycollic  esters  and  study  some 
of  the  reactions  of  this  new  class  of  substituted  acrylic  esters.  (T.  B.  J.) 

2  Ann.  d.  Chem.  (Liebig),  ccxxix,  p.  39;  Behrend  and  Roosen,  ibid.,  ccli, 
P-  239. 


Treat  B.  Johnson  and  Elmer  V.   McCollum   439 

This  method  of  preparation  is  not  suitable  for  preparing  large 
quantities  of  the  acid.  Part  of  the  nitrouracil  is  recovered  in 
the  form  of  a  minouracil,  IX.,  and  the  yield  of  isobarbituric  acid, 
I.,  corresponds  to  only  about  thirty  to  forty-five  per  cent,  of 
the  theoretical. 

NH— CO 

CO      COH  (Yield,  30-45  per  cent.) 
NH— CO  II 

7\  NH— CH 

CO      CNO2  I 

I        II 

NH— CH  NH— CO 

VIII        ^  I        I 

CO      CNH2 

NH— CH 
IX 

When  2-ethylmercapto-5-ethoxy-6-oxypyrimidin,  VI.,  was 
warmed  with  phosphorus  oxychloride,  it  was  converted  smoothly 
into  2-ethylmercapto-5-ethoxy-6-chlorpyrimidin,  X. 

NH— CO  N  =  CC1 

C2H5SC        COC2H5  +  (POC13)   =   C2HSSC        COC2H5 

N  —  CH  N  —  CH 

VI  X 

This  chlorpyrimidin,  X.,  gave  a  theoretical  yield  of  2-ethyl- 
mercapto-5-ethoxy-6-aminopyrimidin,  XI.,  when  heated  with 
strong  alcoholic  ammonia: 

N  =  CC1  N  =  CNH2 

C2H5SC        COC2HS  +  2NH3=  C2HSSC        COC2HS+NH4C1. 


N  —  CH  N  —  CH 

XI 

Especially  interesting  was  the  behavior  of  this  aminopyrimi- 
din,  XL,  towards  hydrochloric  acid.  When  heated  with  this 
reagent,  it  was  converted  into  isobarbituric  acid.  We  have 
investigated  the  mechanism  of  this  reaction  and  find  that  it 
involves  the  formation  of  several  intermediate  compounds. 
We  have  succeeded  in  isolating  each  intermediate  product  of 
the  reaction. 

2-Ethylmercapto-5-ethoxy-6-aminopyrimidin,     XI.,    is    first 


440  Researches  on  Pyrimidins 

converted  into  2-oxy-5-ethoxy-6-aminopyrimidin  or  $-ethoxycy- 
tosin,  XII. 

N   =   CNH2  N   =   CNH2 

C2HSSC        COC2H5  +  H2O  =  CO      COC2HS  +C2HSSH 
II          II  II 

N  —  CH  NH— CH 

XII 

5-Ethoxycytosin,  XII.,  then  reacts  in  two  ways,  according  to 
the  strength  of  the  hydrochloric  acid  used,  giving  2,5-dioxy-6- 
aminopyrimidin  or  $-oxycytosw,  XIII.,  and  2,6-dioxy~5- 
ethoxypyrimidin,  XIV.,  as  follows: 

N   =   CNH2  N   =   CNH2 

CO         COC2HS+HC1  (concentrated)  =  CO      COH  +  C2H5C1 

NH— CH  NH— CH 

XII  XIII 

N   =  CNH2  NH  — CO 

CO       COC2H5+HC1  (dilute)    =       CO       COC2HS+NH4C1 

NH— CH  NH  — CH 

XIV 

5-Oxycytosin,  XIII.,  and  2,  6-dioxy-5-ethoxypyrimidin,  XIV., 
then  react  with  an  excess  of  hydrochloric  acid  to  form  isobar- 
bituric  acid  according  to  the  following  equations: 

N  =  CNH2 

CO      COH  +  H20  +  HC1 

II  x  NH— CO   +  NH4C1 

NH— CH  |          I 

XIII  CO  —  COH 

I          II 
NH— CO  /j  NH— CH   +  C2HSC1 

CO     COC2HS+HC1 

NH— CH 
XIV 

The  sodium  salt  of  ethyl-or-ethoxy-/3-oxyacrylate,  V.,  can 
also  be  used  for  preparing  5-oxy-derivatives  of  isocytosin.1 
Dr.  C.  O.  Johns  finds  that  this  salt  condenses  with  guanidin  to 

1Wheeler  and  Johnson,  A mer.  Chem.  Jour.,  xxix,  p.  492,  1903. 


Treat  B.  Johnson  and  Elmer  V.   McCollum   441 

give  2-amino-5-ethoxy-6-oxypyrimidin  or  $-eihoxyisocytosin,  XV. 
NH2  ;_COOC2H5  NH— CO 

H2NC   +    COC2H5     =     NH2.C        COC2HS +NaOH  +  C2HsOH 

NH        CHONa  N  —  CH 

XV 

We  shall  continue  the  study  of  these  interesting  pyrimidin 
derivatives  in  this  laboratory. 

EXPERIMENTAL    PART. 

Sodium  Salt  of  Ethyl-a-ethoxy-p-oocyacrylate, 

NaO.CH:C(OC2H5).COOC2H5. 

This  salt  was  prepared  by  slowly  adding  to  ether,  in  which  was 
suspended  the  calculated  quantity  of  sodium,  a  mixture  of 
molecular  proportions  of  ethylformate  and  the  ethyl  ester  of 
ethylglycollic  acid.  The  condensation  proceeded  smoothly  with 
evolution  of  hydrogen  gas.  In  the  course  of  8  to  12  hours,  the 
sodium  all  dissolved.  We  made  no  attempts  to  isolate  the 
sodium  salt.  It  was  hydroscopic  and  very  soluble  in  ether. 
After  the  condensation  was  complete,  the  excess  of  ether  was 
evaporated  in  a  partial  vacuum  and  the  crude  salt  dissolved 
in  water.  This  aqueous  solution  was  used  for  experiments  that 
we  describe  in  this  paper.  We  have  assumed,  for  the  purpose 
of  calculation,  that  the  yield  of  sodium  salt  corresponds  to  about 

oo  per  cent,  of  the  theoretical. 

NH— CO 

2  -Ethylmercapto-$-ethoxy-6-oxy pyrimidin,     C2H5SC       COC2H 

N  — CH 

This  pyrimidin  was  prepared  as  follows:  80  grams  of  the  hydro- 
bromic  acid  salt  of  pseudoethylthiourea  were  dissolved  in  about 
150  c.c.  of  cold  water  and  added  to  a  strong  aqueous  solution 
containing  two  molecular  proportions  of  the  sodium  salt  of  ethyl- 
#-ethoxy-/3-oxyacrylate.  This  solution  was  then  combined 
with  50  c.c.  of  water  containing  a  molecular  proportion  of 
potassium  hydroxide  (24.5  grams).  The  mixture  was  then 
thoroughly  shaken;  allowed  to  stand  one  hour  at  ordinary 
temperature,  and  then  heated  on  the  steam-bath  for  another 
hour.  It  was  then  thoroughly  cooled  and  acidified  with  acetic 
acid.  An  excess  of  acetic  acid  should  be  avoided  as  the  pyrim- 


442  Researches  on   Pyrimidins 

idin  is  somewhat  soluble  in  this  reagent.  The  mercaptopyrim- 
idin  separated  at  once  as  a  brown,  crystalline  product.  The 
crude  material  melted  at  i6o°-i65°  C.  The  yield  was  50  grams, 
or  6 1  per  cent,  of  the  theoretical,  calculating  from  the  weight  of 
pseudothiourea  used.  This  yield  of  pyrimidin  was  not  increased 
when  we  used  more  than  a  one-half  molecular  proportion  of  the 
hydrobromic  acid  salt  of  the  pseudothiourea  for  the  condensa- 
tion. Long  standing  of  the  alkaline  solution  also  does  not 
increase  the  yield  of  pyrimidin.  In  one  experiment  the  solution 
was  divided  into  three  equal  parts  and  treated  as  follows:  one 
part  was  warmed  immediately  on  the  steam-bath  for  one  hour 
and  then  acidified  with  acetic  acid;  the  second  part  was  allowed 
to  stand  two  hours,  and  the  third  twenty-four  hours  before 
warming  on  the  steam-bath  and  acidifying  with  acetic  acid.  The 
yields  of  pyrimidin  from  the  three  equal  portions  were  practically 
the  same.  The  pyrimidin  is  difficultly  soluble  in  hot  water  and 
practically  insoluble  in  the  cold.  It  deposited  from  hot  alcohol 
in  rhombic-shaped  prisms  and  melted  at  169°  C.  to  a  clear  oil. 
Analysis  (Kjeldahl)  : 

0.4170  gram  of  substance  gave  0.05712  gram  of  nitrogen  =  40.8  c.c. 
j^  normal  HC1. 

Calculated   for    C<JH12O2N2S:  Found. 

N  =  14 .  oo  per  cent.  *3  •  7°  per  cent. 

Action  of  Hydrochloric  Acid  on  2-Ethylmercapto-$-ethoxy-6- 
oxy  pyrimidin. — The  mercapto-radical  in  this  pyrimidin  is  very 
firmly  bound  and  cannot  be  removed  in  the  usual  manner  by 
boiling  with  hydrochloric  acid.  The  mercaptopyrimidin  was 
recovered  unaltered  after  boiling  for  several  hours  with  this  acid. 
It  was  also  recovered  unaltered  (melting  at  168°  C.)  after  boiling 
with  redistilled  hydrobromic  acid  for  six  hours. 

Action  of  Twenty  Per  Cent.  Hydrochloric  Acid  at  150°  C. — Ten 
grams  of  the  mercaptopyrimidin  were  heated  with  an  excess 
of  twenty  per  cent,  hydrochloric  acid  for  four  hours  at  150-155° 
C.  When  the  tube  was  opened  there  was  considerable  pressure 
due  to  the  presence  of  ethylchlori.de  and  ethylmercaptan  floated 
on  the  surface  of  the  liquid.  A  colorless,  crystalline  product 
was  suspended  in  the  solution.  It  was  insoluble  in  cold  water. 
It  deposited  from  hot  water  in  the  form  of  balls  of  microscopic 
prisms.  It  had  no  definite  decomposition  point  and  did  not 
contain  sulphur.  A  nitrogen  determination  indicated  a  mixture 


Treat  B.  Johnson  and  Elmer  V.   McCollum    443 

of  isobarbituric  acid  and  2,  6-dioxy-5-ethoxypyrimidin.     Analy- 
sis (Kjeldahl): 

0.1363  gram  of  substance  gave  0.02646  gram  of  nitrogen  =  18.9  c.c. 
TV  normal  HC1. 

Calculated  for  C4H4O3N2.      Calculated  for  C6H8O3N2.  Found. 

N  =  21. 87  per  cent.  17.92  per  cent.  19. 3  per  cent. 

We  did  not  have  enough  material  to  separate  the  ethoxy- 
derivative  sufficiently  pure  for  analysis.'  In  order  to  separate 
the  isobarbituric  acid  from  any  ethoxy-derivative  the  mixture 
was  dissolved  in  boiling  acetic  anhydride.  Upon  cooling  the 
acetyl-derivative l  of  isobarbituric  acid  was  obtained  in  the  form 
of  well-developed  prisms.  It  crystallized  from  hot  water  in 
the  form  of  radiating  prisms.  Analysis  (Kjeldahl): 

o.  1162  gram  of  substance  gave  0.01897  gram  of  nitrogen  =  13.55  c-c- 
TV  normal  HC1. 

Calculated    for    C6H6O4N2.  Found. 

N  =  16.47  per  cent.  16.33  per  cent. 

Action  of  Concentrated  Hydrochloric  Acid  at  150°  C. — When  the 
mercaptopyrimidin  was  heated  with  concentrated  hydrochloric 
acid,  it  was  converted  smoothly  into  isobarbituric  acid.  Four 
grams  of  the  mercaptopyrimidin  were  heated  with  concentrated 
hydrochloric  acid  for  three  hours  at  145°  to  155°  C.  When  the 
tube  was  opened  there  was  great  pressure  (ethylchloride)  and 
ethylmercaptan  was  recognized  by  its  stench.  The  solution 
was  evaporated  to  dryness  to  remove  the  excess  of  hydrochloric 
acid.  The  crytalline  residue  was  then  purified  for  analysis  by 
repeated  recrystallizations  from  hot  water  It  separated  in 
corpuscular  crystals  and  decomposed  above  300°  C.,  without 
melting.  A  nitrogen  determination  agreed  with  the  calculated 
in  isobarbituric  acid. 

0.0590  gram  of  substance  gave  0.01288  gram  of  nitrogen  =  9.2  c.c. 
j1^  normal  HC1. 

Calculated  for  C4H4O3N2.  Found. 

N  =  2 1 . 8  7  per  cent.  21.83  Per  cent. 

N   =   CC1 

I  I 

2-Ethylmercapto-$-ethoxy-6-chlorpyrimidin,  C2H5SC        COC2H5 

N  —  CH 

Thirty    grams    of    2-ethylmercapto-5-ethoxy-6-oxypyrimidin 
1  Behrend  and  Roosen,  loc.  cit. 


444  Researches  on  Pyrimidins 

were  warmed  with  50  c.  c.  of  phosphorus  oxychloride.  Hydro- 
chloric acid  began  to  be  evolved  immediately,  and  after  heating 
a  few  minutes  on  the  steam-bath  the  reaction  was  complete. 
The  excess  'of  phosphorus  oxychloride  was  then  removed  by 
heating  at  100°  C.  under  diminished  pressure.  We  obtained  a 
double  compound  of  phosphorus  oxychloride  and  the  chlorpy- 
rimidin  that  was  not  decomposed  by  cold  water.  It  was  insoluble 
in  water  and  did  not  solidify  on  standing.  In  order  to  isolate 
the  chlorpyrimidin  it  was  necessary  to  decompose  the  phos- 
phorus compound  with  hot  water.  By  this  treatment  the 
chlorpyrimidin  was  obtained  as  an  oil  which  finally  solidified. 
It  was  dissolved  in  ether;  the  ethereal  solution  dried  over  cal- 
cium chloride  and  purified  by  distillation  under  diminished 
pressure.  Almost  the  entire  product  boiled  constant  at  185° 
C.  under  a  pressure  of  25  millimeters.  On  cooling,  it  crystallized 
in  beautiful,  radiating  prisms  which  melted  at  44°-46°  C.  It 
crystallized  from  ligroin  in  well  developed  prisms  that  melted  at 
46°  C.  The  chloride  could  be  boiled  with  water  for  hours  with- 
out any  apparent  change.  It  was  soluble  in  cold  alcohol  and 
benzene.  The  yield  of  distilled  product  was  24  grams  or  73  per 
cent,  of  the  theoretical.  Analysis  (Kjeldahl) : 

0.2446  gram  of  substance  gave  0.03*68  gram  of  nitrogen  =  22.  c.c. 
^  normal  HCL 

0.1605  gram  substance  gave  18.9  c.c.  nitrogen  gas  at  24°  and  757  mm. 

Found. 
Calculated  for  C8HUON2SC1.  i.  n. 

N  =  12.81  percent.  I2-S9       13.1  per  cent. 

N   =   CNH2 

I  I 
2-Ethylmercapto-<-ethoxy-6-aminopyrimidin,C2'R5SC       COC2HS 

II  II 
N  —  CH 

Fourteen  grams  of  2-ethylmercapto-5-ethoxy-6-chlorpyrimidin 
were  heated  with  an  excess  of  concentrated  alcoholic  ammonia 
for  three  hours  at  150°-! 60°  C.  Under  these  conditions  the 
aminopyrimidin  was  obtained  as  a  well  crystallized  solid.  It 
was  insoluble  in  cold  water  and  alcohol.  It  deposited  from  hot 
water  or  alcohol  in  rhombic-shaped  prisms  that  melted  at  105° 
C.  to  a  clear  oil.  The  yield  was  quantitative.  When  we  at- 
tempted to  prepare  this  base  by  heating  with  alcoholic  ammonia 


Treat  B.  Johnson  and  Elmer  V.   McCollum    445 

at    i2o°-i3o°    C.    about   one-half   of   the    chlorpyrimidin   was 
recovered  unaltered.     Analysis: 

Calculated  for  CgHt  3 ON3S.  Found. 

N  =  2 1 . 10  per  cent.  2 1 .  oo  per  cent. 

Action  of  Twenty  Per  Cent.  Hydrochloric  Acid  on  2-Ethyl- 
mercapto-  5  -ethoxy-6-aminopyrimidin : 

NH— CO 

2,6-Dioxy-$-ethoxypyrimidin,        CO      COC2H5 

NH— CH 

Three  grams  of  the  aminopyrimidin  were  heated  in  a  sealed 
tube  with  an  excess  of  20  per  cent,  hydrochloric  acid  for  four 
hours  at  150°-!  60°  C.  When  the  tube  was  examined  there  was 
little  pressure  and  drops  of  mercaptan  were  suspended  in  the 
liquid.  The  solution  was  filtered  and  allowed  to  evaporate 
spontaneously  in  a  vacuum.  After  about  three-fourths  of  the 
liquid  had  evaporated,  a  small  amount  of  crystalline  material 
separated.  This  was  filtered  off  and  crystallized  from  hot 
water.  It  deposited  in  balls  of  microscopic  prisms  and  agreed 
in  its  behavior  with  that  of  isobarbituric  acid.  We  did  not 
obtain  sufficient  material  for  analysis.  The  acid  filtrate  was 
evaporated  on  the  steam-bath  to  about  10  c.c.  On  cooling,  a 
well-crystallized  product  deposited.  This  was  filtered  off  and 
the  filtrate  saved  (see  5-ethoxycytosin.)  It  crystallized  from 
hot  water  in  aggregates  of  radiating  prisms.  It  began  to  turn 
brown  at  about  220°  C.  and  then  decomposed  from  260°  to  280° 
C.  with  effervescence  according  to  the  rate  of  heating.  It  was 
insoluble  in  acids  and  did  not  respond  to  a  test  for  sulphur. 
Analysis  (Kjeldahl): 

0.088 1  gram  of  substance  gave  0.01617  gram  of  nitrogen  =  n.  5  c.  c. 
TV  normal  HC1. 

Calculated  for  C6H8O3N2.  Found. 

N  =  17  . 94  per  cent  18 . 3  per  cent. 

N   =   CNH2 

2-Oxy-$-ethoxy-6-aminopyrimidin         ^Q      ^QQ  -^ 
($-Ethoxycytosin) ,  U 

NH  —  CH 

The  acid  filtrate,  after  filtering  from  the  2,  6-dioxy-5~ethoxy- 
pyrimidin  described  above,  was  allowed  to  evaporate  to  dryness 
at  ordinary  temperature.  There  remained  a  crystalline  residue 


446  Researches  on  Pyrimidins 

which  dissolved  in  cold  water  to  a  clear  solution.  When  this 
was  made  distinctly  alkaline  with  ammonium  hydroxide,  we 
obtained  a  beautiful  deposit  of  slender  prisms.  They  melted 
sharply  at  300°  C.  to  a  black  oil.  The  compound  was  very 
soluble  in  warm  water.  It  was  free  from  sulphur  and  did  not 
contain  water  of  crystallization.  Analysis: 

Calculated  for  C6H9O2N3.  Found. 

N  =  27.oQ  percent.  27.22  per  cent. 

Pier  ate  of  $-Eihoxycytosin. — This  was  obtained  when  picric 
acid  was  added  to  a  solution  of  the  base.  It  deposited  in 
characteristic,  arborescent  crystals,  When  slowly  heated,  it 
melted  at  229°-23i°  C.  to  a  clear  oil.  Analysis: 

Calculated  for  C6H9O2N3 . C6H3O7N3.  Found. 

N  =  21. 87  per  cent.  22  .00  per  cent. 

Action  of  Concentrated  Hydrochloric  Acid  on  2-Ethylmercapto- 

5  -ethoxy-6-aminopyrimidin  \ 

N  =   CNH2 

2,  $-Dwocy-6-aminopyrimidin  ($-Oxycytostn)  CO      COH 

NH— CH 

Three  grams  of  2-ethylmercapto-5-ethoxy-6-aminopyrimidin 
were  heated  in  a  sealed  tube  with  concentrated  hydrochloric 
acid  at  150°  C.  for  two  hours.  When  the  tube  was  opened  there 
was  great  pressure  (ethylchloride)  and  a  strong  odor  of  ethyl- 
mercaptan.  The  contents  of  the  tube  were  evaporated  on  the 
steam-bath  to  a  syrup  and  then  dissolved  in  10  c.c.  of  cold  water. 
When  this  aqueous  solution  was  made  alkaline  with  ammonia 
we  obtained  a  crystalline  precipitate.  It  was  purified  by  first 
boiling  with  alcohol  to  remove  any  unaltered  mercaptopyrim- 
idin  and  then  crystallizing  from  water.  It  deposited  in  prismatic 
crystals  that  did  not  melt  below  280°  C.  On  account  of  the 
small  amount  obtained  of  the  base,  we  were  unable  to  free  it 
from  impurities.  Nevertheless  a  nitrogen  determination  indi- 
cated that  we  were  dealing  with  a  2,  5-dioxy-6-aminopyrimidin: 

Calculated  for  C4H5O2N3.  Found. 

N  =  33  .o  per  cent.  32  .  20  per  cent. 

This  experiment  was  repeated  under  the  following  conditions: 
Five  grams  of  the  mercaptopyrimidin  were  heated  with  concen- 
trated hydrochloric  acid  for  three  hours  at  150°-! 60°  C.  Ethyl- 
chloride  and  ethylmercaptan  were  formed  as  in  the  previous 


Treat  B.  Johnson  and  Elmer  V.   McCollum   447 

experiment.  The  contents  of  the  tube  were  evaporated  to 
dryness  on  the  steam-bath.  We  obtained  a  crystalline  residue 
that  partly  dissolved  in  cold  water.  The  insoluble  material 
was  filtered  off  and  crystallized  from  hot  water.  It  was  diffi- 
cultly soluble  and  deposited  on  cooling  in  balls  of  microscopic 
prisms.  It  had  no  definite  melting  point  and  did  not  contain 
sulphur.  A  nitrogen  determination  agreed  with  the  calculated 
value  in  isobarbituric  acid. 

Calculated  for  C4H4O3N,7.  Found. 

N  =  21. 87  per  cent.  22. 3  percent. 

The  aqueous  filtrate  above,  after  filtering  from  isobarbituric 
acid,  was  made  alkaline  with  ammonium  hydroxide.  We 
obtained  no  precipitate  at  first,  but  after  a  few  hours  microscopic 
prisms  deposited  which  were  identified  as  isobarbituric  acid. 
The  alkaline  solution  was  again  filtered  and  then  combined  with 
a  strong  solution  of  picric  acid.  We  obtained  a  well- crystallized 
picrate.  It  deposited  from  hot  water  in  well-developed  prisms 
arranged  in  crosses.  When  heated  in  a  capillary  tube  it  sintered 
above  220°  C.,  then  slowly  decomposed  above  240°  C.  but  did  not 
effervesce  at  270°  C.  It  was  free  from  sulphur  and  did  not 
contain  water  of  crystallization.  A  nitrogen  determination 
agreed  with  the  calculated  value  in  the  picrate  of  2,5-dioxycy- 
tosin  (Kjeldahl): 

0.1067  gram  of  substance  gave  0.02506  gram  of  nitrogen  =  17.9  c.c. 
^  normal  HC1. 

Calculated  for  C4HSO2N3 .  C6H3O:N3.  Found. 

N  =23  . 59  per  cent.  23  . 48  per  cent. 

NH— CO 
I 

2-Methylmercapto-$-ethoxy-6-oxypyr/imidin,    CH3SC        COC2H5 

N  — CH 

Seventy-five  grams  of  the  hydriodic  acid  salt  of  pseudomethyl- 
thiourea  were  dissolved  in  water  and  added  to  a  solution  of 
120  grams  of  the  sodium  salt  of  ethyl-^-ethoxy-/3-oxyacrylate. 
To  this  solution  was  then  added  a  molecular  proportion  of 
potassium  hydroxide  (19.5  grams)  which  was  first  dissolved  in 
water.  The  mixture  was  then  allowed  to  stand  for  four  hours; 
warmed  on  the  steam-bath  for  one  hour,  and  then  acidified 
with  acetic  acid.  The  solution  was  then  concentrated  to 
about  one-half  its  original  volume  and  thoroughly  cooled.  The 


448  Researches  on  Pyrimidins 

mercapto-pyrimidin  deposited  in  the  form  of  prisms.  The  yield 
of  crude  material  was  40  grams.  It  was  insoluble  in  cold 
water.  It  crystallized  from  hot  alcohol  or  water  in  stout  pris- 
matic crystals  that  melted  at  190°  C.  to  a  clear  oil.  Analysis 
(Kjeldahl): 

o.  1811  gram  of  substance  gave  0.02667  gram  of  nitrogen  =  19.05  c.c. 
^  normal  HC1. 

Calculated  for  C7H10O2N2S.  Found. 

N  =  15  . 05  per  cent.  14.  73  per  cent. 

BY  CARL  O.  JOHNS. 

NH— CO 

2-Amino-$-ethoxy-6-oxypyrimidin,     H2N— C        COC2HS 

N CH 

Eighty-two  grams  of  guanidin  carbonate  were  dissolved  in 
water  and  combined  with  a  solution  of  150  grams  of  barium 
hydroxide.  The  barium  carbonate  was  filtered  off  and  the 
clear  filtrate  containing  guanidin  was  added  to  an  aqueous 
solution  of  90  grams  of  the  sodium  salt  of  ethyl- <*-ethoxy-/3- 
oxy  aery  late.  The  mixture  was  then  allowed  to  stand  for 
twenty-four  hours.  When  it  was  neutralized  with  acetic  acid 
no  precipitate  was  obtained.  The  solution  was  then  concen- 
trated on  the  steam-bath  and  the  base  precipitated  with  a  cold, 
saturated  solution  of  mercuric  chloride.  This  was  filtered  off, 
washed  with  cold  water,  and  decomposed  with  hydrogen  sul- 
phide. The  mercury  sulphide  was  removed  by  filtration  and 
the  clear  filtrate  evaporated  to  dryness.  We  obtained  a  dark 
colored  residue  which  was  dissolved  in  water  and  boiled  with 
animal  charcoal  to  remove  the  color.  When  this  solution  was 
neutralized  with  ammonia,  the  pyrimidin  base  separated  in  the 
form  of  distorted  prisms.  It  formed  a  very  insoluble  sulphate 
that  crystallized  from  hot,  dilute  sulphuric  acid  in  well  developed 
prisms.  They  decomposed  at  22^-226°  C.  with  effervescence 
and  contained  two  molecules  of  water  of  crystallization: 

0.8588  gram  of  substance  lost  0.0700  gram  of  H2O  at   no°-i2o°C. 
Calculated  for  (C6H9O2N3)2  .H2SO4 .  2H2O.  Found. 

H2O=8.n  per  cent.  8.18  per.  cent. 

Nitrogen  determination  in  the  hydrous  salt  (Kjeldahl):    0.1037  gram 
of  salt  gave  0.01960  gram  of  nitrogen  =   14  c.c.  -j^  normal  HC1. 
Calculated  for  (C6H9O2N3)2  .H2SO4.2H2O.  Found. 

N  =  18 . 9  per  cent.  .  18.9  per  cent. 

Nitrogen  determination    in  the  anhydrous  salt    (Kjeldahl):      0.1255 


Treat  B.  Johnson  and  Elmer  V.   McCollum   449 

gram  of  salt  gave  0.02548  gram  of  nitrogen  =  18.2  c.c.  TV  normal  HC1. 
Calculated  for  (C6H9O2N3)  2 .  H2SO4.  Found. 

N  =  20.58  percent.  20.31  per  cent. 

The  pyrimidin  base  was  isolated  in  a  pure  state  when  this 
sulphuric  acid  salt  was  digested  in  water  with  barium  carbonate. 
The  excess  of  barium  carbonate  and  barium  sulphate  was  re- 
moved by  nitration  and  the  nitrate  evaporated  to  dryness. 
The  base  was  obtained  in  the  form  of  distorted  prisms.  It 
deposited  from  hot  water  in  microscopic  prisms  which  melted 
at  248°  C.  to  a  clear  oil.  Analysis  (Kjeldahl): 

0.0978  gram  of  substance  gave  0.02618  gram  of  nitrogen  =18.7  c.c. 
t^  normal  HC1. 

Calculated  f or  C6  H9  O ,  N3 .  Found. 

N=27.o9  percent.  26.77  per  cent. 


[Reprinted  from  the  American  Chemical  Journal,    Vol.  XXXVI,    No.  2 
August,  1906.] 


Contributions  from  the  Sheffield  Laboratory  of  Yale  University. 

CXXXL— RESEARCHES  ON  PYRIMIDINES  :  THE  AC- 
TION OF  POTASSIUM  THIOCYANATE  UPON 
IMIDE  CHLORIDES. 

[FIFTEENTH  PAPER.] 

BY  TREAT  B.  JOHNSON  AND  ELMER  V.  MCCOLLUM. 

We  shall  describe  in  this  paper  a  new  case  of  the  molecular 
rearrangement  of  a  thiocyanate,  I.,  to  an  isothiocyanate,  II., 
which  is  unique  for  this  type  of  metamerism. 

RSCN    •*-     RNCS. 
I.  II. 

In  the  acyclic  series  an  unsaturated  condition  in  the  2,3-posi- 
tion 

C  :  CC 

3  2    I 

is  favorable  for  the  formation  of  isothiocyanates.  For  example : 
Allyliodide,  III.,  and  1,2-dichlorpropylene,1  IV.,  when  heated 
with  potassium  thiocyanate,  react  to  form  the  corresponding 
isothiocyanates,  according  to  the  following  equations  : 

CH2  :  CHCH2I  +  KSCN     = 

III. 
KI  -j-  CH2  :  CHCH2SCN     «~     CH2  :  CHCH2NCS  ; 

CH2  :  CC1CH2C1  +  KSCN     = 
IV. 

KC1  +  CH2  :  CC1CH2SCN    ~-     CH2  :  CC1CH2NCS. 

Such  groupings,  so  far  as  examined,  do  not  permit  of  the 
isolation  of  the  primary  products— thiocyanates — except  when 
heat  is  avoided. 

In  a  recent  publication  from  this  laboratory,  Wheeler  and 
Bristol2  have  described  the  behavior  of  some  cyclic  imide  chlor- 
ides towards  potassium  thiocyanate.  Since  such  chlorides, 
V.,  are  closely  related  to  acid  chlorides,  VI.,  and  the  cyclic 

1  Wheeler  and  Merriam  :  J.  Am.  Chem.  Soc.,  33,  287. 

2  THIS  JOURNAL,  33,  448  (1905). 


Researches  on  Pyrimidines.  137 


—  CCl  :  NR,  —  CC1  :  O, 

V.  VI. 

derivatives  examined  contain  an  unsaturated  2,3-position,  VII., 

C1CCX  :  CH 
i  ___  i 

VII. 

it  seemed  probable  that  isothiocyanates  would  result  if  such 
halides  were  treated  with  potassium  thiocyanate. 

Their  experimental  data  supported  this  assumption.  They 
observed  that  2-ethylmercapto-6-chlorpyrimidine,  VIII., 
2-ethylmercapto-5-brom-6-chlorpyrimidine,  IX.,  and  2-ethyl- 
mercapto-5-methyl-6-chlorpyrimidine,  X.,  reacted  with  potas- 
sium thiocyanate,  under  certain  conditions,  to  give  the  corre- 
sponding isothiocyanates.  They  did  not  obtain  any  positive 
evidence  of  the  intermediate  formation  of  thiocyanates  : 

H,CC1  H2CC1 

I  I 
CH                                                   CC1 

II  II 
HCH                                                 HCH 

(  Allylchloride.  )  (  i  ,2-Dichlorpropylene.  ) 

N=    —  CC1  N=    mCCl 

II  II 

C2H5SC  CH  C,H6SC  CBr 


CH  N CH 

XI. 

We  had  occasion  to  examine,  in  the  course  of  our  work,  the 
behavior  of  2-ethylmercapto-5-ethoxy-6-chlorpyrimidine,1  XI., 
towards  potassium  thiocyanate.  On  account  of  the  close 
analogy  of  this  imide  chloride  to  those  examined  by  Wheeler 

1  Johnson  and  McCollum  :  J.  Biolog.  Chem.,  i,  437  (1906). 


138  Johnson  and  McCollum. 

and  Bristol,1  we  expected  that  it  would  react  in  a  similar  man- 
ner to  form  an  isothiocyanate.  We  find  that  this  chloride, 
XI.,  reacts  smoothly  with  potassium  thiocyanate,  in  an  alco- 
holic solution,  to  give  a  normal  rhodanide,  XII.,  as  repre- 
sented in  the  following  equation  : 


I  I 

C2H5SC  COC2H5  +  KSCN     = 

II  II 
N  -  CH 

N.  -  CSCN 


C2H6SC          COC2H5  +  KC1. 


That  a  thiocyanate  is  the  primary  product  of  this  reaction, 
we  have  established  in  the  following  manner :  It  did  not 
give  thiourea  derivatives  with  ammonia  or  organic  bases. 
It  reacted  quantitatively  with  thiobenzoic  and  thioacetic 
acids  to  give  the  same  2-ethylmercapto-5-ethoxy-6-thio- 
pyrimidine,  XIV.  This  reaction  with  thioacids  involves  the 
intermediate  formation  of  2-ethylmercapto-5-ethoxy-6-benzoyl- 
mercaptopyrimidine,  XIII.,  and  2-ethylmercapto-5-ethoxy-6- 
acetylmercaptopyrimidine,2  XV.,  which  then  undergo  hy- 
drolysis to  the  thiopyrimidine,  XIV. 

We  find  that  2-ethylmercapto-5-ethoxy-6-thiocyanpyrimi- 
dine,  XII.,  shows  no  tendency  to  rearrange  to  the  isothiocyan- 
ate,8 XVI.,  at  the  ordinary  temperature.  On  the  other  hand, 
if  heated  above  100°  it  is  transformed  quantitatively  into  its 
isomer,  XVI.  The  thiocyanate  can  be  recrystallized  from 
alcohol,  but  on  prolonged  boiling  it  partially  rearranges  to  the 
isothiocyanate.  This  combines  at  once  with  the  alcohol  to 
form  a  urethane,  XVII. 

1  Loc.  ctt. 

a  Wheeler  and  Merriam :  THIS  JOURNAL,  23,  283  (1901). 

8  Samples  of  the  thiocyanate  that  had  been  preserved  for  five  months  showed  no 
change  in  melting  point.  We  shall  keep  specimens  for  an  indefinite  period  in  order 
to  see  whether  any  rearrangement  will  take  place  at  the  ordinary  temperature. 

T.  B.  J. 


Researches  on  Pyrimidines. 


139 


O 

w 


8 

•8 


o 

B 

8 

w 
W 


P 

n 


a=- 
0=0— 


i 

03 
W 


w 


•f 


M   f 

H=0J  H; 


p 

w 

3-0—3 


M 


o 
o 


o 
W 


\  ^ 

I 


I 

o 
o 
w 


w 

CO 

o 


P 

W 


dl  ;   | 
•O-| 


o 

° 
o 


140  Johnson  and  McCollum. 

CNCS 

C2H5OH 


JN 

UoUJN 

IN             V-  IN  L  D 

1 

1 

1                1 

C2H6SC 

COC2H5    »-»- 

C2H6SC           COC2H6 

II 

II 

II            II 

N— 

—  CH 

N  CH 

XVI. 

f°\  XT  T  T  /~\  C\  /"\  /~\    TV 

CNHCSOC  H5 

1 

C2H6SC 

COC2H5 

N CH 

XVII. 

It  seems  very  probable  to  the  writers  that  the  imide  chlor- 
ides examined  by  Wheeler  and  Bristol1  will  give  thiocyanates 
if  treated  with  potassium  thiocyanate  under  the  proper  condi- 
tions. Judging  from  the  properties  of  2-ethylmercapto-5- 
ethoxy-6-thiocyanpyrimidine,  XII.,  their  thiocyanates  would 
be  expected  to  undergo  a  rearrangement  under  the  conditions 
employed  in  their  experiments. 

These  four  imide  chlorides  constitute  an  ideal  series  with 
which  to  test  the  rule  as  to  whether  the  tendency  for  a  thio- 
cyanate to  rearrange  to  an  isothiocyanate  is  proportional  to  the 
negative  character  of  the  alkyl  group.  The  only  difference  in 
structure  is  the  character  of  the  radicals  occupying  the  5-posi- 
tion.  If  the  tendency  to  form  isothiocyanates  is  directly  pro- 
portional to  the  negative  influence  of  these  four  radicals,  evi- 
dently the  negative  character  of  the  pyrimidines  in  question 
must  be  expressed  by  the  following  arrangement  : 

C1CC(CH3)  :  CH  ;  C1CCH  :  CH  ; 

C1CC(OC2H5)  :  CH  ;  CICCBr  :  CH. 

i I  I 1 

That  the  negative  influence  of  the  radicals  occupying  the 
5-position  is  to  be  represented  by  the  arrangement — CH3,  H, 
OC2H5,  Br — is  shown  on  substituting  these  groups  in  acetic 
acid  and  comparing  the  affinity  constants2  of  the  resulting 
acids. 

» Loc.  cit. 

»Ostwald  :  Phys.  Chem.,  3, 174-184. 


Researches  on  Pyrimidines.  141 

CH3CH2COOH,  HCH2COOH, 

K  =  0.00134  K  =  0.0018 

C2H6OCH2COOH,  BrCH2COOH. 

K  =  0.0234  K  —  0.138 

The  affinity  constant  in  the  case  of  acetic  acid  is  decreased 
by  the  introduction  of  the  methyl  radical,  while  by  the  substi- 
tution of  the  more  negative  ethoxy  group  it  is  increased  in 
the  proportion  1:13.  The  investigation  of  these  thiocyanate 
derivatives  is  now  in  progress  in  this  laboratory. 

EXPERIMENTAL,  PART. 

2-Ethylmercapto-5-ethoxy-6-thiocyanpyrimidine, 

N=CSCN 

I  I 

C,H5SC  COC2H6.  —Twenty-one  grams  of  2-ethylmercapto- 

II  II 
N  --  CH 

5-ethoxy-6-chlorpyrimidine1  and  n  grams  of  potassium  thio- 
cyanate were  dissolved  in  95  per  cent  alcohol  and  the  solution 
boiled  for  6  hours.  Potassium  chloride  began  to  separate  im- 
mediately on  warming  and  by  prolonged  boiling  the  alcoholic 
solution  assumed  a  red  color.  After  the  completion  of  the  re- 
action the  excess  of  alcohol  was  removed  by  evaporation  and 
the  residue  treated  with  cold  water,  to  extract  the  potassium 
chloride  and  the  excess  of  potassium  thiocyanate.  We  ob- 
tained a  well  crystallized  product  that  was  soluble  in  hot  alco- 
hol and  benzene.  It  deposited  from  alcohol  in  lemon-yellow 
prisms,  which  melted,  at  66°-67°,  to  a  clear  oil.  When 
heated  above  its  melting  point  it  showed  no  signs  of  decompo- 
sition below  200°.  It  was  insoluble  in  alkali  and  was  not 
changed  when  warmed  with  aqueous  ammonia.  It  possessed 
the  properties  of  a  weak  base.  It  dissolved  in  strong  hydro- 
chloric acid  and  was  reprecipitated  unaltered  by  alkali  or  by 
dilution  with  water.  Analysis  (Kjeldahl)  : 

Calculated  for 

Found. 


N  17-42  17.12 

1  Johnson  and  McCollum  :  J.  Biolog.  Chem.,  i,  443  (1906). 


142  Johnson  and  McCollum. 

Action  of  Thiobenzoic  Acid  and  Thioacetic  Acid  on  2-Ethylmer- 

capto-5-ethoxy-6-thiocyanpyrimidine. 

Two  and  five-tenths  grams  of  the  thiocyanate  were  dissolved 
in  one  molecular  proportion  of  thiobenzoic  acid.  The  sub- 
stances reacted  at  once  with  the  evolution  of  considerable  heat. 
After  warming  for  a  few  minutes  in  a  boiling  water-bath,  to  com- 
plete the  reaction,  the  product  was  treated  with  a  little  alcohol, 
when  it  crystallized  in  the  form  of  well  developed,  yellow 
prisms.  It  was  purified  for  analysis  by  crystallization  from 
alcohol.  It  melted,  at  i44°-i45°,  to  a  clear  oil.  Nitrogen 
determinations  agreed  with  the  calculated  value  in  2-ethyl- 
mercapto-5-ethoxy-6-thiopyrimidine  (see  below)  : 

Calculated  for  Found. 

C8HlsONaS2.  I.  II.  III. 

N  12.96  13.2         12.88         13.2 

Two  grams  of  the  thiocyanate  were  dissolved,  at  the  ordi- 
nary temperature,  in  i  molecular  proportion  of  thioacetic 
acid.  After  a  few  minutes  heat  began  to  be  evolved  and  the 
mixture  solidified.  It  was  then  warmed  in  a  boiling  water- 
bath  for  a  few  minutes.  The  product  crystallized  from  95  per 
cent  alcohol  in  yellow  prisms  and  melted,  at  i44°-i45°,  to  a 
clear  oil.  When  this  material  was  mixed  with  some  of  the 
compound  obtained  by  the  action  of  thiobenzoic  acid  on  the 
thiocyanate,  and  heated  in  a  capillary  tube,  the  melting  point 
was  not  lowered.  The  two  substances  were  identical.  We 
did  not  detect  the  formation  of  any  carbon  bisulphide  in  these 
reactions  with  thioacids.1  When  the  mother  liquors  were 
treated  with  a  solution  of  ferric  chloride  we  obtained  charac- 
teristic, red  colored  solutions,  showing  the  presence  of  free 
thiocyanic  acid.  Analysis  (Kjeldahl)  : 

Calculated  for 
C8HuON2Sa.  Found. 

N  12.96  13.2 

2-Ethylmercapto-5-ethoxy-6-thiopyrimidine, 
NH CS 

I  I 

C2H5SC          COC2H6.— For  the  purpose  of  identification  this 

II  II 
N CH 

1  Wheeler  and  Merriam :  J.  Am.  Chein.  Soc.,  33,  284. 


Researches  on  Pyrimidines ,  143 

compound  was  prepared  by  boiling  2-ethylmercapto-5-ethoxy- 
6-chlorpyrimidine  with  an  alcoholic  solution  of  potassium  hy- 
drosulphide.  The  reaction  was  smooth  and  potassium  chlor- 
ide precipitated  at  once  from  the  alcohol.  When  the  solution 
was  acidified  with  acetic  acid  the  pyrimidine  separated  as  a 
yellow,  crystalline  substance.  It  deposited  from  alcohol  in 
prisms  and  melted,  at  144°-! 45°,  to  a  clear  oil.  When  this 
material  was  mixed  with  the  compounds  obtained  in  the  reac- 
tions with  thioacids,  described  above,  the  melting  point  was 
not  changed.  Analysis : 

Calculated  for 
C8H12ONjS2.  Found. 

N  12.96  13.2 

2-Ethylmercapto-5-ethoxy-6-isothiocyanpyrimidine, 
N rCNCS 

C2H5SC  COC2H5.— 2-Ethylmercapto-5-ethoxy-6-thiocyan- 

II  II 

N CH 

pyrimidine  shows  no  tendency  to  rearrange  into  the  isothio- 
cyanate  at  ordinary  temperatures.  In  order  to  decide  at  what 
temperature  this  rearrangement  would  take  place  we  performed 
the  following  experiments  :  One  gram  of  the  thiocyanate 
was  heated  in  a  sulphuric  acid-bath,  at  8o°-9o°,  for  i  hour. 
On  cooling,  the  material  crystallized  immediately.  It  melted, 
at  66°-67°,  to  a  clear  oil  and  was  identified  as  the  unaltered 
thiocyanate.  It  was  then  heated  for  another  hour  at  9O°-ioo°. 
The  material  solidified  on  cooling  and  melted  sharply  at  66°- 
67°.  It  was  then  heated  for  3  hours  at  io5°-uo°.  On  cooling 
the  material  refused  to  solidify  and,  after  standing  for  several 
days,  still  retained  the  consistency  of  a  syrup.  That  this 
product  was  an  isothiocyanate  was  proved  as  follows  :  It  re- 
acted at  once  with  ammonia  to  give  practically  a  quantitative 
yield  of  2-ethylmercapto-5-ethoxy-6-thioureapyrimidine  (see 
below)  which  melted,  at  i7i°-i72°,  to  a  clear  oil. 

In  order  to  obtain  the  isothiocyanate  sufficiently  pure  for 
analysis,  10  grams  of  the  thiocyanate  were  distilled  under  di- 
minished pressure.  Much  decomposition  took  place,  but  we 


144  Johnson  and  McCollum. 

obtained  a  fraction  boiling  at  228°-235°  (20-23  mm.).  This 
oil  was  exceedingly  hygroscopic  and  weighed  5  grams.  When 
allowed  to  stand  in  a  desiccator,  over  concentrated  sulphuric 
acid,  it  finally  solidified.  It  was  exceedingly  soluble  in  the 
common  organic  solvents  and,  when  exposed  to  the  air,  began 
to  assume  an  oily  appearance.  The  crude  material  melted,  at 
45°-5o°,  to  a  turbid  oil.  Analysis  (Kjeldahl)  : 

Calculated  for 
C9HnON8Sa.  Found. 

N  17.4  16.8 

Two  attempts  were  made  to  prepare  this  isothiocyanate  by 
boiling  a  mixture  of  the  chlorpyrimidine,  toluene  and  potas- 
sium thiocyanate.  In  our  first  experiment  10  grams  of  the 
chlorpyrimidine  and  5.5  grams  of  potassium  thiocyanate  were 
taken  and  the  mixture  boiled  for  12  hours.  Under  these  con- 
ditions we  observed  no  evidence  of  any  reaction.  We  then 
boiled  a  mixture  of  5  grams  of  the  chlorpyrimidine,  2.3  grams 
of  potassium  thiocyanate  and  toluene  for  30  hours.  On  evap- 
orating the  excess  of  toluene  and  crystallizing  the  residue 
from  petroleum  ether,  we  recovered  4  grams  of  the  unaltered 
chloride  melting  at  44°. 

2-Elhylmercapto-5-ethoxy-6-thioureapyrimidine, 
N=CNHCSNH2 

I  I 

C2H6SC  COC»H5          .—This  thiourea  was  formed  read- 

II  II 

N CH 

ily  when  the  isothiocyanate  above  described  was  treated  with 
aqueous  ammonia.  It  deposited  from  hot  alcohol  in  slender, 
yellow  prisms,  that  melted  at  172°,  without  effervescence,  to  a 
clear  oil.  Analysis  (Kjeldahl)  : 

Calculated  for 
C9H14ON4S2.  Found. 

N  21.70  21.47 

2-Ethylmercapto-5-ethoxy-6-thionethylurethanepyrimidine, 

. 2-Ethylmercapto-5-ethoxy-6- 


Researches  on  Pyrimidines.  145 

thiocyanpyrimidine  undergoes  a  rearrangement  into  the  iso- 
meric  isothiocyanate  derivative  when  boiled  with  alcohol. 
Thirty-five  grams  of  2-ethylmercapto-5-ethoxy-6-chlorpyrimi- 
dine  and  20  grams  of  potassium  thiocyanate  were  dissolved  in 
95  per  cent  alcohol  and  the  solution  boiled  for  n  hours* 
When  we  evaporated  the  alcohol  and  treated  the  residue  with 
cold  water,  to  remove  potassium  chloride  and  potassium  thio- 
cyanate, we  obtained  a  semi-solid  which  showed  no  signs  of 
crystallizing  after  standing  for  3  hours.  This  material  was 
then  treated  with  a  dilute  solution  of  sodium  hydroxide.  We 
observed  that  part  of  the  substance  dissolved  in  the  alkali  and 
the  insoluble  portion  assumed  a  crystalline  form.  This  was 
filtered  off  and  recrystallized  from  alcohol.  It  deposited  in 
prisms  that  melted  at  66°-67°.  It  was  identified  as  the  thio- 
cyanate. Analysis  (Kjeldahl)  : 

Calculated  for 
CgHnONaSs.  Found. 

N  1742  17.16 

The  urethane  that  was  dissolved  by  the  alkali  was  recov- 
ered when  we  acidified  the  solution  with  hydrochloric  acid. 
It  separated  in  light  yellow  prisms.  It  was  insoluble  in  hot 
and  cold  water  and  very  soluble  in  hot  alcohol.  It  deposited 
from  alcohol  in  long  prisms,  which  showed  signs  of  melting  at 
89°  and  then  melted  at  93°-94°,  to  an  oil.  The  yields  of  thio- 
cyanate and  urethane  were  about  equal.  Analysis  (Kjeldahl): 

Calculated  for 

CnH1702N8S2.  Found. 

N  14.63  14.85 

In  order  to  study  the  velocity  of  the  rearrangement  of  the 
thiocyanate  into  its  isomer  in  boiling  ethyl  alcohol,  we  per- 
formed the  following  experiments  :  Fifteen  grams  of  2-ethyl- 
mercapto-5-ethoxy-6-chlorpyrimidine  and  9  grams  of  potas- 
sium thiocyanate  were  boiled  in  alcohol  for  24  hours.  After 
separating  the  urethane  from  the  thiocyanate  in  the  usual  way 
and  then  recrystallizing  the  compounds  from  alcohol,  we  ob- 
tained 1.2  grams  of  the  thiocyanate  and  10  grams  of  the  ureth- 
ane. In  a  second  experiment  we  used  15  grams  of  the  chlor- 
pyrimidine,  9  grams  of  potassium  thiocyanate  and  boiled  the 


146  Johnson  and  McCollum. 

alcoholic  solution  4  hours.  We  obtained  10  grams  of  thio- 
cyanate  or  60.6  per  cent  of  the  theoretical,  and  i  .3  grams  of 
urethane.  In  no  case  did  our  combined  yields  of  thiocyanate 
and  urethane  correspond  to  more  than  60-70  per  cent  of  the 
theoretical.  In  order  to  demonstrate  that  this  loss  is  due  to 
the  fact  that  the  urethane  slowly  volatilizes  when  the  alcoholic 
solutions  are  evaporated,  we  performed  the  following  experi- 
ment: An  alcoholic  solution  of  15  grams  of  the  imide  chlor- 
ide and  6.6  grams  of  potassium  thiocyanate  was  boiled  for  30 
hours.  The  alcoholic  solution  was  then  treated  with  a  molec- 
ular proportion  of  sodium  ethylate,  to  form  a  sodium  salt  of  the 
urethane  and  evaporated  to  dryness.  We  obtained  4.9  grams 
of  thiocyanate.  The  urethane  was  obtained  by  neutralizing  its 
sodium  salt  with  acetic  acid  and  weighed  9.85  grams.  These 
yields  accounted  for  95.26  per  cent  of  the  imide  chloride  used 
in  the  experiment. 

2-Ethy!mercapto-5-ethoxy-6-thionpropylurethanepyrimidine, 
N=rCNHCSOC8H, 

C.H.SC          COC.H,  .—This  urethane  was  formed  when 

II  II 

N  -  CH 

3  grams  of  2-ethylmercapto-5-ethoxy-6-chlorpyrimidine  and  2 
grams  of  potassium  thiocyanate  were  dissolved  in  normal 
propyl  alcohol  and  the  solution  boiled  for  6  hours.  Under 
these  conditions  we  did  not  obtain  any  thiocyanate.  The  ureth- 
ane was  purified  by  recrystallizing  from  95  per  cent  alcohol. 
It  deposited  in  small  prisms  that  melted,  at  56°-57°,  without 
effervescence,  to  a  clear  oil.  Analysis  (Kjeldahl): 

Calculated  for 

CiaHiaOjNsSj.  Found. 

N  13.95  13-76 

2-Ethylmercapto-5-ethoxy-6-phenylthioureapyrimidine, 


C,H6SC          COC2H6  .—The  common  method  of  pro- 

N  -  CH 
cedure  in  the  preparation  of  the  thioureas  described  in  this 


Researches  on  Pyrimidines.  147 

paper  was  to  heat  the  2-ethylmercapto-5-ethoxy-6-thiocyan- 
pyritnidine  iu  an  oil-bath  at  i5O°-i6o°,  for  about  30  minutes 
and  thoroughly  rearrange  it  to  the  isothiocyanate.  This  was 
then  dissolved  in  a  little  benzene  and  combined  with  a  molecu- 
lar proportion  of  the  organic  base.  The  reactions  were  usually 
accompanied  with  evolution  of  heat  and  the  yields  of  thioureas 
were  practically  quantitative. 

The  phenylthiourea  derivative  was  soluble  in  hot  alcohol 
and  insoluble  in  water.  It  deposited  from  alcohol  in  distorted 
prisms  and  melted,  at  82°-83°,  to  a  clear  oil.  Analysis  (Kjel- 
dahl)  : 

Calculated  for 
Ci6H18ON4S2.  Found. 

N  16.76  16.75 

2-Ethylmercapto-5-ethoxy-6-paratolylthioureapyrimidine, 
N=CNHCSNHC6H4CH3 

C2H5SC  COC2H5  .—This  thiourea  was  insol- 

II  II 

N CH 

uble  in  water.  It  was  soluble  in  hot  alcohol  but  insoluble  in 
cold .  It  deposited  from  alcohol  in  clusters  of  needles  radia- 
ting from  a  common  center.  They  melted,  at  115°,  to  a  clear 
oil,  without  effervescence.  Analysis  (Kjeldahl)  : 

Calculated  for 
Ci6H2oON4S2.  Found. 

N  16.09  16.20 

2-Ethylmercap  to- 5-  ethoxy-6-orthotolylthioureapyrimidine, 
N==zCNHCSNHC6H,CH3 

C2H5SC          COC2H5  .—This  thiourea  was  insol- 

II  II 

N CH 

uble  in  water  and  soluble  in  warm  alcohol.  It  deposited  from 
alcohol  in  rhombic-shaped  prisms  and  melted,  at  i29°-i3o°,  to 
a  clear  oil. 

Calculated  for 

Ci«H2oON4Sa.  Found. 

N  16.09  15.86 


148  Johnson  and  McCollum. 

2-Ethylmercapto-5-ethoxy-6-paraanisylthioureapyrimidine, 
N=z:CNHCSNHC6H46cH8 

i        I 

C2H6SC  COC2H5  .—From  paraanisidine 

II  II 

N CH 

and  2-ethylmercapto-5-ethoxy-6-isothiocyanpyrimidine.  This 
base  showed  little  tendency  to  react  with  the  isothiocyanate  at 
ordinary  temperatures.  In  order  to  complete  the  action  the 
mixture  was  heated  in  a  boiling  water-bath,  for  6  hours.  The 
product  was  then  washed  with  dilute  hydrochloric  acid  to  re- 
move unaltered  anisidine  and  afterwards  purified  by  crystal- 
lizing from  95  per  cent  alcohol .  It  deposited  from  alcohol  in 
rhombic  prisms  and  melted  at  I22°-I23°.  Analysis  (Kjel- 
dahl)  : 

Calculated  for 

Ci6H2oO2N482.  Found. 

N  15.38  15-53 

2-Et  'iylmercapto-5-  ethoxy-  6-metanitrophenylthioureapyrimidine, 

N==CNHCSNHC6H,NO, 

C2H6SC          COC2H6.  .—  This  thiourea  was  ob- 

II  II 

N CH 

tained  when  i  gram  of  2-ethylmercapto-5-ethoxy-6-isothio- 
cyanate  and  a  molecular  proportion  of  metanitraniline  were 
dissolved  in  benzene  and  digested  on  the  steam-bath,  for  i 
hour.  When  the  benzene  was  evaporated  the  thiourea  re- 
mained as  an  oil,  which  soon  solidified.  It  was  insoluble  in 
hot  water  and  slightly  soluble  in  alcohol.  It  crystallized  from 
benzene  in  the  form  of  slender  prisms  which  melted,  at 
161°,  without  effervescence,  to  a  clear  oil.  Analysis  (Kjel- 
dahl) : 

Calculated  for  Found. 

C16H17O3N5S2.  I.  II.  III.  IV. 

N  18.47  18.23     18.23     18.09     18.10 

NBW  HAVBN,  CONN., 
May  5,  1906. 


[Reprinted  from  the  American  Chemical  Journal,    Vol.  XXXVI,    No.  2. 
August,  1906.] 


Contributions  from  the  Sheffield  Laboratory  of  Yale  University. 

CXXXII.— RESEARCHES  ON  PYRIMIDINES  :  ON  THE 

FORMATION  OF  PURINES  FROM  UREA- 

PYRIMIDINES. 

[SIXTEENTH  PAPER.] 

BY  TREAT  B.  JOHNSON  AND  KLMER  V.  MCCOLLUM. 

It  has  been  shown  by  several  investigators1  that  5-urea- 
pyrimidines,  in  which  the  4  and  6  positions  are  occupied  by 
oxygen,  I.,  condense  to  purines  when  heated  with  oxalic  or 
hydrochloric  acids.  The  condensation  of  2,4,6-trioxy-5-urea- 
pyrimidine  (pseudouric  acid),  I.,  to  uric  acid,2  II.,  represents 
the  simplest  case  of  this  method  of  purine  formation. 

NH — CO  NH CO 

II  II 

CO        CHNHCONH2     =     CO       C— NH 

||  |  || 

NH CO  NH C— NH 

I.  II. 

On  the  other  hand,  5-ureapyrimidines,  III.,  IV.,  in  which 
hydrogen  or  an  alkyl  radical  occupies  the  4-position,  show  no 
tendency  to  undergo  a  similar  condensation  when  treated  with 
dehydrating  agents.  Behrend3  obtained  no  evidence  of  the 
formation  of  purines  when  2,6-dioxy-5-ureapyrimidine  (hy- 
droxyxanthine),  III.,  and  2,6-dioxy-4-methyl-5-ureapyrimi- 
dine  (methylhydroxyxanthine),  IV.,  were  treated,  under 
various  conditions,  with  phosphorus  pentachloride,  sulphuric 
acid,  acetic  anhydride  and  chlorsulphonic  acid. 


XI  -i-A 

io 


NH CO  NH CO 

I  I  I 

CNHCONH2,  CO        CNHCONH,. 

I            II                                          I  II 

NH CH  NH CCH, 

III.  IV. 

1  Fischer  and  Ach  :  Ber.  d.  chem.  Ges.,  38,  2473.    Fischer:  Ibid.,  30,   559;   33, 
1701.    Sembritski :  Ibid.,  30,  1814.    Armstrong  :  Ibid.,  33,  2308. 

2  Fischer  and  Ach  :  Loc.  cit. 

»  Ann.  Chem.  (^iebig),  229,  40  ;  231,  248,  251 ;  240,  i. 


150  Johnson  and  McCollum. 

This  observation  of  Behrend's  was  later  confirmed  by  Wid- 
man.1  He  investigated  the  behavior  of  2,6-dioxy-5-ureapyrimi- 
dines,  V.,  towards  potassium  hydroxide.  On  account  of  the 
structural  relationship  between  such  ureapyrimidines  and  acyl- 
semicarbazides,  VI.,  it  was  important  to  compare  their  be- 
havior towards  this  reagent.  He  found  that  the  ureapyrimi- 
dines, V.,  could  be  recovered  unaltered  after  warming  with 
dilute  solutions  of  potassium  hydroxide,  while  the  acylsemi- 
carbazides,  VI.,  condensed  smoothly  to  triazoles,2  VII. 

RN CO  RCO  RC=N 

I  I 


CO       CNHCONH,,         NNHCONH, 


CO. 


RN CH  C6H5  C6H6N NH 

V.  VI.  VII. 

On  account  of  the  pronounced  difference  in  behavior  of  4,6- 
dioxy-5-ureapyrimidines  from  6-oxy-5-ureapyrimidines,  III. 
and  IV. ,  it  seemed  desirable  to  prepare  a  5-hydroxy-6-urea- 
pyrimidine,  VIII.  It  was  of  interest  to  decide  whether  such  a 
ureapyrimidine  derivative  would  undergo  an  inner  condensa- 
tion to  form  a  purine. 

N CNHCONH, 

I  I 
RC          COH 

II  II 
N CH 

VIII. 

We  have  selected  as  a  suitable  representative  of  this  new  class 
of  hydroxyureapyrimidines  2-ethylmercapto-5-ethoxy-6-urea- 
pyrimidine,  X.  The  structural  relationship  between  this 
pyrimidine  and  Behrend's  hydroxyxanthine,  III.,  is  illustrated 
by  representing  the  oxygen  derivative  in  its  enol  form,  IX.  : 
N=  =COH  N CNHCONH2 

II  II 

HOC          CNHCONH,,       C2H5SC          COC2H6 

II  II  '    II  II 

N CH 

IX.  X. 

1  Ber.  d.  chem.  Ges.,  29,  1954  (1896). 

2  Widman  :  Ber.  d.  chem.  Ges.,  29,  1946. 


Researches  on  Pyrimidines.  151 

We  have  prepared  this  urea  derivative,  X.,  in  the  following 
manner  :  When  2-ethylmercapto-5-ethoxy-6-thionethylureth- 
anepyrimidine,1  XI.,  was  treated  with  molecular  proportions 
of  sodium  ethylate  and  ethyl  bromide,  it  gave  2-ethylmercapto- 
5-ethoxy-6-iminothioethylcarbonatepyrimidine,  XII.  : 

N=CNHCSOC1H6 

C2H5SC  COC2H5  +  NaOC2H6  +  C2H6Br     = 

II  II 

N CH 

XI. 

N CN  :  C(OC2H6)SC,H5 

C2H5SC          COC,H6  4-  NaBr  -f  C3H5OH. 

II  II 

N CH 

XII. 

This  iminothiocarbonate,  XII.,  evolved  ethylmercaptan 
when  treated  with  alcoholic  ammonia  and  was  converted,  prac- 
tically quantitatively,  into  2-ethylmercapto-5-ethoxy-6-pseudo- 
ethylureapyrimidine,  XIII.  : 

N CN  :  C(OC2H6)SC,H6 

C2H6SC          COC2H6  -f  NHS    = 

II  II 

N CH 

N CN  :  C(OC2H6)NH2 

I  I 

C2H6SC          COC2H6  +  C2H6SH. 

II  II 
N CH 

XIII. 

This  pseudourea,  XIII.,  then  gave  the  normal  urea,  X., 
when  treated  with  cold,  concentrated  hydrochloric  acid  : 

N CN  :  C(OC2H6)NH2 

I  I 

C2H6SC          COC2H5  +HaO     = 

II  II 
N CH 

1  Johnson  and  McCollum :  THIS  JOURNAL,  36,  136  (1906). 


152  Johnson  and  McCollum. 

N: CNHCONH, 

I  I 

C2H5SC  COC2H5  +  C2H6OH. 

II  II 

N CH 

x. 

Attempts  to  condense  the  pseudourea,  XIII.,  or  the  normal 
urea,  X. ,  to  purine  derivatives  were  without  success.  Sodium, 
in  boiling  benzene,  attacked  the  pseudoureapyrimidine,  XIII., 
to  form  a  cyanaminopyrimidine,  XIV.  When  the  normal 
ureapyrimidine,  X.,  was  treated  in  the  same  manner  it  was 
recovered  unaltered.  It  underwent  decomposition  when 
heated  above  its  melting  point : 
N=  =CN  :  C(OC2H5)NHa 

+  Na     = 


N=CNHCN 

I  I 

C2H5SC  COC2H5   +  C2H5OH. 


The  5-ethoxy  radical  in  the  above  ureapyrimidines,  XIII., 
and  X.,  apparently  is  as  firmly  linked  as  the  bromine  atoms  in 
the  5-brom-6-ureapyrimidines  that  were  examined  by  Wheeler 
and  Bristol.1  They  were  unable  to  condense  2-ethylmercapto- 
5-brom-6-pseudoethylureapyrimidine,  XV.,  or  2-ethylmer- 
capto-5-brom-6-ureapyrimidine,  XVI.,  to  purine  derivatives. 
The  bromine  atom  in  these  compounds  could  not  be  removed 
by  heating  with  pyridine,  or  by  digesting  in  benzene  with  me- 
tallic sodium  : 


CN:C(OC2H5)NH2  N=   =CNHCONHa 


II 
C,H6SC  CBr  ,     C2H6SC  CBr 

II  II 

N  --  CH 

XV. 
i  THIS  JOURNAL,  33,  448  (1905). 


Researches  on  Pyrimidines .  153 

In  this  paper  we  also  describe  a  series  of  substituted 
6-aminopyrimidines  that  we  have  prepared  by  warming 
2-ethylmercapto-5-ethoxy-6-chlorpyrimidine1  with  organic 
bases.  These  derivatives  are  characterized  by  their  stability 
towards  boiling  acids.  2-Ethyltnercapto-5-ethoxy-6-paratolu- 
idinopyrimidine,  XVII.,  could  be  boiled  with  concentrated 
hydrochloric  acid  without  removing  the  mercapto  radical. 


i                     4 

/""\  "XTT  T  /"A    TT    /~\TT 

' 

CNHC6H4CH, 

C2H5SC 

II 

1 
COC2H6 

II 

II 
N  — 

II 
—  CH 

XVII. 


EXPERIMENTAL. 

Dieihylformylglycollate,    C2H5OCH(CHO)COOC,H6. The 

sodium  salt  of  this  ester  was  described  in  a  previous  paper  by 
Johnson  and  McCollum.2  We  now  find  that  the  free  ester  can 
easily  be  prepared  from  this  sodium  salt.  It  separated  as  a 
colorless  oil  when  an  aqueous  solution  of  the  sodium  salt  was 
acidified  with  hydrochloric  acid.  It  was  purified  by  fractional 
distillation,  under  diminished  pressure.  A  fraction  that  dis- 
tilled at  ii5°-ii8°  (35  mm.)  was  used  for  the  analytical  de- 
terminations. 

I.  0.4711  gram  substance  gave  0.8763  gram  CO2  and  0.3190 
gram  H2O. 

II.  0.4732  gram  substance  gave  0.8 85 3  gram  CO2  and  0.3 176 
gram  H2O. 

III.  0.4677   gram   substance  gave  0.8762   gram   CO2   and 
0.3121  gram  H2O. 

Calculated  for  Pound. 

C7H12O4.  I.  II.  III. 

C  52.5  5°-72         51-02         51-09 

H  7-5  7-33          7-45  7-4i 

1  Johnson  and  McCollum  :  Loc.  cit. 

2  J.  Biolog.  Chem.,  i,  437. 


154  Johnson  and  McCollum. 

NH — CO 

2y6-Dioxy-5-ethoxypyrimidine,  CO        COC2H,.  —  This   com- 

I  II 

NH CH 

pound  was  described  in  a  previous  publication  by  Johnson  and 
McCollum.1  It  was  obtained,  associated  with  isobarbituric 
acid,  when  2-ethylmercapto-5-ethoxypyrimidine  was  heated  in 
a  sealed  tube,  with  hydrochloric  acid.  We  find  that  this  pyr- 
imidine  can  easily  be  prepared  by  boiling  2-methylmercapto- 
5-ethoxypyrimidine2  with  hydrochloric  acid.  It  agreed  in  its 
properties  with  the  compound  described  in  our  former  paper. 
Analysis  (Kjeldahl)  : 

Calculated  for 

CeH8OsN2.  Found. 

N  17.95  18.00 

2-Ethylmercapti-5-ethoxy-6-iminothioethylcarbonatepyrimidine, 
N CN  :  C(OC2H5)SC2HB 

C2H6SC  COC2H6  .—Twelve  grams  of  2-ethyl- 

II  II 

N CH 

mercapto-5-ethoxy-6-thionethylurethanepyrimidine2  were  dis- 
solved in  alcohol  containing  one  molecular  proportion  of  metal- 
lic sodium.  Four  and  five-tenths  grams  of  ethyl  bromide 
were  then  added  and  the  solution  allowed  to  stand  at  the  ordi- 
nary temperature  until  neutral  to  litmus.  After  the  reaction 
was  complete  the  excess  of  alcohol  was  evaporated  on  the 
steam-bath,  and  the  oily  residue  treated  with  cold  water  to  re- 
move sodium  bromide.  An  oil  was  obtained  which  was  ex- 
tracted with  ether  and  dried  over  calcium  chloride.  When  the 
ether  was  evaporated,  the  diethylcarbonate  remained  as  an  oil 
which  would  not  solidify.  Analysis  (Kjeldahl)  : 

Calculated  for 

Ci3H2102N3S2.  Found. 

N  13.33  12.94 

i  Loc.  cit. 

*  Johnson  and  McCollum  :  Loc.  cit. 


Researches  on  Pyrimidines.  155 

2-Ethylmercapto-5-ethoxy-6-pseudoethylureapyrimidine, 
N CN  :  C(OC2H6)NH2 

C2H6SC  COC2H5  .—This  derivative  was   ob- 

I!          II 

N CH 

tained  when  dry  ammonia  gas  was  passed  into  an  alcoholic 
solution  of  the  above  iminothioethylcarbonate.  When  the 
alcoholic  solution  was  evaporated  to  dryness  the  pseudourea 
was  obtained  as  a  well  crystallized  compound.  It  was  very 
soluble  in  alcohol  and  benzene  and  was  purified  for  analysis  by 
recrystallizing  from  ligroin.  It  melted,  at  77°,  to  a  clear  oil. 
Analysis  (Kjeldahl)  : 

Calculated  for 
CnHi8O2N4S.  Found. 

N  20.74  20.40 

2-Ethylmercapto-5-ethoxy-  6-ureapyrimidine, 
N=CNHCONH3 

C2H5SC          COC,H5         .—This  urea  was  obtained  when  the 

II  II 

N CH 

above  pseudourea  was  allowed  to  stand  dissolved  in  concentra- 
ted hydrochloric  acid.  After  remaining  a  few  days,  the  urea 
was  precipitated  by  adding  water.  It  was  readily  soluble  in 
hot  alcohol  and  deposited  from  cold  alcohol  in  prismatic  crys- 
tals, which  melted  at  i66°-i67°,  with  slight  effervescence,  to  a 
clear  oil.  It  gave  a  strong  test  for  sulphur,  but  did  not  con- 
tain chlorine.  When  mixed  with  2-ethylmercapto-5-ethoxy-6- 
oxypyrimidine1  (m.  p.  i66°-i67°)  the  melting  point  was  low- 
ered to  1 40°- 1 43°.  Analysis  (Kjeldahl)  : 

Calculated  for 
C9HMOSN4S.  Found. 

N  23.14  23.17 

One  gram  of  this  urea  and  i .  5  grams  of  metallic  sodium  were 
suspended  in  benzene  and  the  mixture  boiled  for  20  hours. 
There  was  no  evidence  of  any  reaction  except  that  the  sodium 

1  Johnson  and  McCollum  :  Loc.  cit. 


156  Johnson  and  McCollum. 

became  coated  with  a  thin  deposit.  When  the  benzene  was 
evaporated  and  the  sodium  dissolved  in  alcohol,  we  obtained  a 
crystalline  deposit  that  melted  at  about  166°.  It  crystallized 
from  hot,  95  per  cent  alcohol  in  prisms  that  melted  at  166°- 
167°,  with  slight  effervescence.  It  was  identified  as  the  unal- 
tered urea.  We  did  not  observe  the  formation  of  the  cyan- 
aminopyrimidine  (see  below).  Analysis  (Kjeldahl)  : 

Calculated  for 

Found. 


N  23.14  23.07 

2-Ethylmercapto-5-ethoxy-6-cyanaminopyrimidinet 
N=CN  :  C  :  NH 

C»H6SC          COC.H,          .—About   i   gram    of    2-ethylmer- 

'    II  II 

N  -  CH 

capto-5-ethoxy-6-pseudoethylureapyrimidine  was  dissolved  in 
dry  benzene  and  treated  with  a  slight  excess  over  one  molecu- 
lar proportion  of  metallic  sodium.  The  mixture  was  then 
boiled  for  40  hours.  The  sodium  underwent  a  complete  change 
by  this  treatment  and  was  transformed  into  a  slimy  precipitate. 
On  filtering  and  evaporating  the  benzene  there  was  no  residue. 
The  precipitate  that  remained  on  the  filter  was  dissolved  in 
alcohol  and  the  solution  evaporated  to  dryness.  The  residue 
was  then  dissolved  in  cold  water.  When  this  solution  was 
acidified  with  acetic  acid  a  white,  crystalline  product  separated 
in  the  form  of  prisms.  The  substance  melted  sharply  at  167°- 
168°,  with  only  slight  effervescence.  It  was  soluble  in  alkali 
and  was  reprecipitated  by  acids.  It  was  insoluble  in  cold,  but 
readily  soluble  in  hot  water  and  alcohol.  When  dissolved  in 
boiling  water  it  slowly  decomposed.  On  cooling  it  deposited 
in  prismatic  crystals  that  melted  at  about  i65°-i66°.  When 
the  cyanamide  derivative  (m.  p.  i67°-i68°)  was  mixed  with 
the  above  urea  (m.  p.  i66°-i67°)  the  melting  point  was  lowered 
to  i48°-i55°.  Analysis  (Kjeldahl)  : 

Calculated  for 
C9Hi2ON4S.  Found. 

N  25.00  24.95 


Researches  on  Pyrimidines.  157 

About  0.5  gram  of  the  cyanamide  derivative  was  allowed  to 
stand  dissolved  in  a  few  cc.  of  concentrated  hydrochloric  acid. 
A  deposit  of  slender  prisms  was  obtained  which  gave  a  strong 
test  for  chlorine.  They  melted  at  i75°-i8o°,  with  violent 
effervescence,  and  had  all  the  properties  of  a  hydrochloric  acid 
salt.  On  treating  with  dilute  ammonia  they  completely  dis- 
solved, but  on  standing  the  solution  deposited  prismatic  crys- 
tals that  melted  at  i66°-i67°.  This  was  identified  as  2-ethyl- 
mercapto-5-ethoxy-6-ureapyrimidine.  When  it  was  mixed 
with  this  urea  the  melting  point  was  not  lowered. 

2-Ethylmercapto-5-ethoxy-6-aniinopyrimidine, 
N CNHC6H5 

I  I 

CSH5SC          COC2H5     .—This  base  was  obtained   when   an 

II  II 
N CH 

alcoholic  solution  of  3  grams  of  2-ethylmercapto-5-ethoxy-6- 
chlorpyrimidine  and  2.8  grams  of  aniline  were  boiled  for  24 
hours.  It  was  insoluble  in  water  and  very  soluble  in  alcohol. 
It  deposited  from  ligroin  in  large  prisms,  which  melted  at  60°. 
Analysis  (Kjeldahl)  : 

Calculated  for 
Ci4H1:ON3S.  Found. 

N  15.27  15.19 

2-Ethylmercapto-5-ethoxy-6-paratoluidinopyrimidine, 
N=CNHC6H4CH3 

C2H6SC          COC2H6  .—This  base  was  obtained  as  an  oil 

II  II 

N CH 

when  an  alcoholic  solution  of  2-ethylmercapto-5-ethoxy-6- 
chlorpyrimidine  and  the  calculated  quantity  of  paratoluidine 
was  boiled  for  10  hours.  It  formed  a  well  crystallized  hydro- 
chloride,  that  deposited  from  water  in  hair-like  crystals  and 
melted  at  io5°-io6°,  with  effervescence.  Analysis  (Kjeldahl) : 

Calculated  for 
C16H19ON3S.HC1.  Found. 

N  12.90  12.71 


158  Johnson  and  McCollum. 

When  the  hydrochloride  was  treated  with  dilute  ammonia 
the  free  base  precipitated  as  an  oil.  It  was  soluble  in  ether 
and  ligroin.  It  deposited  from  ligroin  in  long  prisms,  that 
melted  at  72°.  Analysis  (Kjeldahl)  : 

Calculated  for 
Ci6H19ON3S.  Found. 

N  14.53  H.57 

This  mercaptopyrimidine  can  be  boiled  with  concentrated 
hydrochloric  acid  without  decomposition.  After  boiling  0.7 
gram  with  an  excess  of  hydrochloric  acid,  for  12  hours,  it  was 
recovered  unaltered  and  melted  sharply  at  72°. 

2-Ethylmercapto-5-ethoxy-6-orthotoluidinopyrimidine, 
N=CNHCSH4CH3 

C.H.SC          COC3H6  .—From  orthotoluidine  and  2-ethyl- 

II  II 

N CH 

mercapto-5-ethoxy-6-chlorpyrimidine.  Its  hydrochloric  acid 
salt  crystallized  from  alcohol  in  prisms,  that  decomposed  at 
1 40°- 1 45°.  The  salt  is  not  stable  in  aqueous  solution  and 
dissociates  into  the  base  and  hydrochloric  acid.  Analysis 
(Kjeldahl): 

Calculated  for 
CiBH19ON8S.HCl.  Pound. 

N  12.90  12.30 

The  free  base  is  insoluble  in  water,  and  very  soluble  in  alco- 
hol. It  deposited  from  alcohol  in  flat  prisms,  that  melted  at 
80°.  It  was  insoluble  in  ligroin.  Analysis  (Kjeldahl)  : 

Calculated  for 
C15H19ON3S.  Found. 

N  14.53  14.49 

2-Ethylmercapto-5-ethoxy-6-paraanisidmopyrimidine, 
N=z=CNHC6H4OCH3 

C2H6SC          COC3H§  .  —  From   paraanisidine    and 

II  II 

N CH 

2-ethylmercapto-5-ethoxy-6-chlorpyrimidine.      This    reaction 


Researches  on  Pyrimidines.  159 

was  not  as  smooth  as  those  with  the  preceding  amines.  The 
base  was  first  obtained  as  an  oil  which  would  not  solidify. 
It  was  dissolved  in  dry  benzene  and  the  solution  saturated 
with  dry  hydrochloric  acid  gas.  The  hydrochloride  deposited 
in  prismatic  crystals.  It  was  purified  by  recrystallization  from 
acetone  or  ethyl  acetate  and  was  insoluble  in  benzene  and 
ligroin.  Analysis  (Kjeldahl)  : 

Calculated  for 
C16H19O2N3S.HC1.  Found. 

N  12.29  12.19 

When  the  hydrochloride  was  treated  with  ammonia  the  base 
was  obtained  as  an  oil  which  finally  solidified.  It  deposited 
from  alcohol  in  stout  prisms,  that  melted  at  68°-69°,  without 
effervescence,  to  a  clear  oil.  It  was  insoluble  in  water. 
Analysis  (Kjeldahl)  : 

Calculated  for  Found. 

Ci6H]902N3S.  I.  II. 

N  13.77  13-77  IS-8* 

2-Ethylme,capto-5-ethoocy-6-metanitroaniUnopyrimidine) 
N=CNHC6H4NO2 

C2H5SC          COC2H6.  .—The    hydrochloride  of  this 

II  II 

N CH 

pyrimidine  base  crystallized  from  alcohol  and  melted  at  125°- 
135°,  with  effervescence.  The  base  was  insoluble  in  water. 
It  deposited  from  alcohol  in  long  needles,  which  melted,  at 
125°,  to  a  clear  oil.  Analysis  (Kjeldahl)  : 

Calculated  for 
CHHnjO3N4S.  Found. 

N  17.50  17.13 

NEW  HAVEN,  CONN., 
May  5,  1906. 


[Reprinted  from  the  American  Chemical  Journal,    Vol.  XXXVI,    No.  2 
August,  1906.] 


Contributions  from  the  Sheffield  Laboratory  of  Yale  University. 

CXXXIII.  —  RESEARCHES    ON    PYRIMIDINES  :      ON 

5-NITROCYTOSINE    AND    ITS    REDUCTION 

TO  2-OXY-5,6-DIAMINOPYRIMIDINE. 

[SEVENTEENTH  PAPER.] 

BY  TREAT  B.  JOHNSON,  CARL  O.  JOHNS  AND  FREDERICK  W.  HEYL. 

There  are  five  possible  monooxydiaminopyrimidines  in 
which  the  oxygen  atom  can  occupy  positions  2  and  6,  assum- 
ing that  the  amino  groups  are  attached  to  carbon.  Their  for- 
mulae are  given  below,  I.-V.  Three  of  these  have  been  syn- 
thesized, viz.  :  2,4-diamino-6-oxypyrimidine,1  I.,  2-oxy-4,6-di- 
aminopyrimidine,2  II.,  and  6-oxy-2,5-diaminopyrimidine,5  III. 
In  this  paper  we  shall  describe  the  fourth  member  of  this  series 
— 2-oxy-5,6-diaininopyrimidine,  IV.  : 

NH CO  N=   =CNH2  NH CO 

I  I  I  I  I  I 

HaNC  CH      ,      CO        CH     ,     H2NC          CNH2, 

I!  II          II 

NH CNH,  N CH 

II.  III. 

NH CO 

I  I 

CH       CNH2. 

II  II 
NH CH                         N CNH2 

IV.  V. 

In  a  previous  paper  from  this  laboratory,  Wheeler  and 
Johnson4  have  shown  that  cytosine  is  converted  into  nitrocyto- 
sine  when  treated  with  a  mixture  of  nitric  and  sulphuric  acids. 
No  attempt  was  made  to  establish  the  structure  of  this  nitro 
derivative.  They  assumed,  nevertheless,  on  account  of  the 
unstable  character  of  the  products  formed  on  reduction,  that 
they  were  dealing  with  a  nitramine,  VI.,  instead  of  5-nitrocy- 
tosine,  VII.  : 

1  Traube  :  Ber.  d  chem.  Ges.,  33,  1371. 

2  Wheeler  and  Jamieson  :    THIS  JOURNAL,  32,  342  (1904). 
8  Johnson  and  Johns  :  Ibid.,  34,  554  (1905). 

.,  31,591  (1904). 


Researches  on  Pyrimidines.  161 

CNHN02  N=   =CNH2 


II 
CO        CH  ,  CO       CN02. 

I  II  I  II 

NH  --  CH  NH  -  CH 

VI.  VII. 

In  the  course  of  our  work  on  oxydiaminopyrimidines  it  was 
necessary  to  decide  whether  the  structure  of  nitrocytosine  is  to 
be  represented  by  Formula,  VI.,  or  by  Formula  VII.  If  it  is 
a  5-nitropyrimidine,  VII.,  it  seemed  probable  that  it  might 
give  a  diaminopyrimidine  when  reduced  under  the  proper  con- 
ditions. 

The  nitrocytosine  that  was  used  in  this  research  was  pre- 
pared by  dissolving  2-ethylmercapto-6-aminopyrimidine,1 
VIII.,  in  a  mixture  of  concentrated  nitric  and  sulphuric  acids. 
It  was  converted,  practically  quantitatively,  into  the  same 
nitropyrimidine,  VII.,  as  was  obtained  from  cytosine,2  IX. 


CNH2 

CH      +  HN03  (sp.  gr.  1.5) 


H  ^ 

vin.  CO 

N=   =CNH2  *  | 

|  |  #  NH 

CO        CH      +  HNO,  (sp.  gr.  1.5)  VII. 

I  II 

NH CH 

IX. 

We  now  conclude  that  this  nitro  derivative  is  2-oxy-5-nitro- 
6-aminopyrimidine,  VII.,  and  not  a  nitramine,  VI.,  as  repre- 
sented in  the  previous  paper.2  That  this  conclusion  is  correct 
is  established  by  the  following  data : 

When  nitrocytosine  was  heated  under  pressure,  with  20  per 
cent  sulphuric  acid,  it  was  converted  into  nitrouracil,  X.  : 

1  Wheeler  and  Johnson  :  THIS  JOURNAL,  29/497  (1903). 

2  Wheeler  and  Johnson  :  Loc.  cit. 


162 


N: 


CO 

I 
NH — CH 


Johnson,  Johns  and  Heyl. 

CNH3  NH CO 

CNO2  +  H2O     =     CO        CNO,  +  NHS. 


NH CH 

X. 


This  result  is  analogous  to  those  obtained  when  cytosine 
and  5-methylcytosine1  were  heated  with  sulphuric  acid.  They 
were  converted  into  uracil  and  thymine,  respectively.  While 
this  result  supports  the  assumption  that  the  nitro  group  in 
nitrocytosine  occupies  the  5-position,  yet  there  was  the  possi- 
bility of  the  nitramine,  VI. ,  giving  nitrouracil  under  the  same 
conditions.  This  would  involve  a  rearrangement  of  the  nitro 
group  from  the  amino  radical  to  the  5-position  in  the  pyrimi- 
dine  ring,  and  then  a  hydrolysis  to  nitrouracil,  as  represented 
above  : 


N CNHNO2 

I  I 

CO       CH 

I  II 

NH CH 

VI. 


N= 
CO 


iCNH, 
CN02 


NH — CH 

VII. 


NH CO 

I  I 

CO        CNO2. 

I  II 

NH CH 

x. 


Analogous  rearrangements  have  been  observed  to  take 
place  in  the  benzene  series.  Bamberger2  found,  for  example, 
that  phenylnitramine,  XI.,  was  rearranged  into  orthonitroani- 
line,  XII. ,  when  warmed  with  sulphuric  or  hydrochloric  acids : 


NHNO, 


H 


NH2 


XI. 


XII. 


Although  this  rearrangement  is  theoretically  possible,  yet  it 
did  not  seem  probable  to  the  writers  because  nitrocytosine  is 
prepared  under  conditions  that  are  not  favorable  for  the  forma- 

1  Wheeler  and  Johnson  :  Loc.  ctt. 
*  Her.  d.  Chem.  Ges.  26,  490. 


Researches  on  Pynmidines.  163 

tion  of  a  nitramine.  Furthermore,  we  have  obtained  experi- 
mental evidence  which  shows  that  this  rearrangement  does  not 
take  place. 

It  has  been  observed  by  several  investigators1  that  the  amino 
radical  in  amino  acids  is  replaced  by  chlorine  and  bromine 
when  these  acids  are  treated  with  nitrosyl  chloride  and  nitrosyl 
bromide.  We  have  investigated  the  behavior  of  nitrosyl 
chloride  towards  nitrocytosine  and  find  that  this  pyrimidine  is 
converted  smoothly  into  nitrouracil  when  warmed  with  an 
aqueous  solution  of  the  reagent.2  This  reaction  involves  the 
intermediate  formation  of  2-oxy-5-nitro-6-chlorpyrimidine, 
XIII.  Under  the  conditions  employed  in  our  experiment  this 
imide  chloride,  XIII.,  would  be  decomposed  with  the  produc- 
tion of  nitrouracil  and  hydrochloric  acid,  as  follows  : 

N=  =CNH,  N=   =CC1 

II  II 

CO        CN02-fNOCl     -     CO       CNO,  +  H2O  +  N2; 

I  II                                     I  II 
NH CH                               NH CH 

XIII. 

Nzz  — CC1  NH CO 

II  II 

CO       CNO,  +  HaO     =     CO       CN02  +  HC1. 

I  II  I  II 

NH CH  NH — CH 

It  appears  to  the  writers  that  this  method  of  formation  of 
nitrouracil  from  nitrocytosine  excludes  the  possibility  of  a  re- 
arrangement of  the  nitro  group.  The  conditions  of  the  reac- 
tion are  far  less  favorable  for  a  rearrangement  than  those  em- 
ployed in  the  preparation  of  nitrocytosine  from  2-ethylrner- 
capto-6-aminopyrimidine. 

Furthermore,  the  following  result  would  seem  to  indicate 
that  there  is  no  tendency  for  2-mercapto-6-aminopyrimidines 
to  form  nitramines  even  when  it  is  impossible  for  a  nitro  group 
to  enter  the  5-position  in  the  pyrimidine  ring.  When  2-ethyl- 

1  Tilden  and  Forster  :  J.  Chem.  Soc.,  67,  489.  Tilden  and  Marshall :  Ibid.,  67,  494. 
Walden:  Ber.  d.  chem.  Ges.,  29,  134.  Fischer :  Ann.  Chem.  (I^iebig),  340,  171. 
Stanek  :  2,.  physiol.  Chem.,  46,  263  (1905), 

3  Stanek  :  Loc.  cit, 


i64 


Johnson,  Johns  and  Heyl. 


mercapto-5-brom-6-aminopyrimidine,1  XIV.,  was  dissolved  in  a 
mixture  of  nitric  and  sulphuric  acids  it  was  converted,  smoothly, 
into  5-bromcytosine,2  XV.  We  obtained  no  evidence  of  the 
formation  of  a  nitramine,  XVI. 


N: 

C3H6SC 

II 
N- 


:CNH2 

CBr  +  HN03  (sp.  gr.  1.5) 


XIV. 


=      CO        CBr 

I  II 

NH CH 

XV. 


N CNHNO, 

I  I 

CO       CBr 

I  II 

NH — CH 

im  — 

XVI. 


It  has  been  the  usual  experience,  when  a  pyrimidine  having 
a  hydrogen  atom  in  the  5-position  is  attacked  by  bromine,  that 
this  hydrogen  is  easily  replaced  by  the  halogen.3  We  now 
find  that  bromine  has  no  action  on  nitrocytosine.  This  result 
is  in  accord  with  previous  observations  and  again  indicates  that 
the  nitro  group  occupies  the  5-position  in  this  pyrimidine. 
Behrend4  observed  that  nitrouracil  was  recovered  unaltered 
after  heating  with  liquid  bromine,  at  100°  : 


CO       CNO2  , 

I  II 

NH CH 

(Nitrocytosine. ) 


NH CH 

( Nitrouracil. ) 


The  above  data  and  the  facts  that  nitrocytosine  does  not 

1  Wheeler  and  Johnson :  THIS  JOURNAL,  31,  604. 

2  Wheeler  and  Johnson  :  Loc,  tit, 

3  Wheeler  and  Johnson  :  THIS  JOURNAL,  29,  504.   Ibid.,  31,  603.    Gabriel  and  Col- 
man:  Ber.   d.  chem.  Ges.,  34,  1238.     Wheeler  and  Bristol:  THIS  JOURNAL,  33, 437. 
Johnson  and  Johns  :  Ibid.,  34,  175.   J.  Biolog.  Chem.,  i ,  305. 

*  Ann.  Chem.  (I^iebig),  240,  n. 


Researches  on  Pyrimidines.  165 

give  "  L,iebermann's  reaction,"1  or  Thiele  and  Lachman's2 
"  nitramine  reaction,"  prove  that  nitrocytosine  is  a  2-oxy-5- 
nitro-6-aminopyrimidine,  as  represented  by  Formula  VII. 

We  find  that  5-nitrocytosine  can  be  reduced  with  aluminium- 
amalgam  to  2-oxy-5,6-diaminopyrimidine,  IV.  : 

N=  =CNH2  N=  =CNH2 

II  II 

CO       CNO,  +  3H2     =     CO       CNH3  +  2H,O. 

I            II                                 I  II 

NH CH  NH CH 

IV. 

The  reduction  was  very  smooth,  but  we  encountered  several 
experimental  difficulties  before  we  succeeded  in  isolating  the 
product.  The  base  is  especially  characterized  by  the  ease  with 
which  it  undergoes  decomposition  in  aqueous  solution.  It  is 
the  most  unstable  aminopyrimidine  that  we  have  prepared  in 
this  laboratory.  It  gave  a  very  insoluble  picrate  and  was  pre- 
cipitated from  its  aqueous  solution  by  potassiobismuth  iodide, 
mercuric  chloride  and  phosphotungstic  acid.  Like  2, 5-diamino- 
6-oxypyrimidine,8  it  contained  i  molecule  of  water  of  crystal- 
lization. 

In  this  paper  we  also  describe  a  series  of  substituted  2-ethyl- 
mercapto-6-aminopyrimidines,  XVII.,  that  we  have  prepared 
by  heating  2-ethylmercapto-6-chlorpyrimidine4  with  aromatic 
bases.  These  mercaptopyrimidines  were  converted  into  cyto- 
sine  derivatives,  XVIII.,  when  boiled  with  mineral  acids  : 


N CNHR  Nn   —  CNHR 


CO       CH 

I  II 

-CH  NH CH 

XVII.  XVIII. 

1  Ber.  d.  chem.  Ges.,  7,  248.    Baeyer :  Ibid.,  7,  966.    Mahla  and  Tiemann  :  Jfa'd., 
39,  2810.    Fraiicesconi  and  Angelucci:  Gazz.  chim.  ital.,  31,  II.,  302(1901).    Scholl : 
Ann.  Chem.  (I^iebig),  338,  3  (1904). 

2  Ann.  Chem.  (Uebig),  a88,  269  (1895). 

3  Johnson  and  Johns :  Loc.  cit. 

*  Wheeler  and  Johnson  :  Loc.  cit. 


1 66  Johnson,  Johns  and  Heyl. 

EXPERIMENTAL  PART. 

2-Oxy-5-nitro-6-aminopyrimidine  (5- Nitrocytosine) , 
N CNH2 

I  I 

CO        CNO2 . — This  compound  has  been  described  in  a  pre- 

I  II 

NH CH 

vious  paper.1  It  was  obtained  by  nitrating  cytosine  in  the 
presence  of  sulphuric  acid.  We  find  that  it  can  be  obtained 
very  easily  by  nitrating  2-ethylmercapto-6-aminopyrimidine.2 
The  largest  yield  of  nitrocytosine  was  obtained  when  we  pro- 
ceeded under  the  following  conditions  :  Nineteen  cc.  of  con- 
centrated sulphuric  acid  were  mixed  with  37  cc.  of  nitric  acid 
(sp.  gr.  1.5).  To  this  mixture  were  then  slowly  added  12.5 
grams  of  the  mercaptopyrimidine.  The  reaction  was  very  vio- 
lent and  the  pyrimidine  dissolved  immediately  with  evolution 
of  much  heat.  After  all  the  pyrimidine  had  been  added  the 
solution  was  allowed  to  stand  at  the  ordinary  temperature  for 
about  15-16  hours.  The  mixture  was  then  poured  upon 
crushed  ice  and  the  acids  neutralized  with  concentrated  am- 
monia. The  nitropyrimidine  deposited  from  the  neutral  solu- 
tion as  a  white,  microscopic  powder.  It  was  purified  by  re- 
crystallization  from  hot  water.  We  obtained  10.5  grams  of 
the  nitropyrimidine,  corresponding  to  83.5  per  cent  of  the 
theoretical  yield.  Analysis  (Kjeldahl)  : 

Calculated  for 

C4H4O8N4.  Found. 

N  35.89  35.72 

The  Hydrochloride  of  5- Nitrocytosine. — Nitrocytosine  was  dis- 
solved in  warm,  dilute  hydrochloric  acid.  Upon  cooling,  the 
hydrochloride  deposited  in  clusters  of  needle-like  prisms. 
They  did  not  decompose  below  300°.  Analysis  (Kjeldahl)  : 

Calculated  for 

C4H4O8N4.HC1.  Found. 

N  29.09  29.2 

Behavior  of  ^-Nitrocytosine  when  Heated  with  Sulphuric  Acid 
under  Pressure. — Two  grams  of  5-nitrocytosine  were  heated  in 

i  Wheeler  and  Johnson  :  Loc.  cit. 
8  Wheeler  and  Merriam  :  Loc.  cit. 


Researches  on  Pyrimidines.  167 

a  sealed  tube,  with  20  per  cent  sulphuric  acid,  for  3  hours,  at 
1 85°- 1 97°.  When  the  tube  was  examined  there  was  no  pres- 
sure and  slender  prisms  had  deposited  in  the  acid  solution. 
They  decomposed,  with  effervescence,  at  about  275°-277°. 
The  compound  was  insoluble  in  acids  and  soluble  in  ammonia 
and  in  sodium  hydroxide.  It  gave  no  test  for  sulphuric  acid 
when  warmed  with  a  solution  of  barium  chloride,  and  agreed 
in  its  behavior  with  that  of  nitrouracil.  In  order  to  demon- 
strate that  it  was  nitrouracil  the  material  was  reduced  in  an 
ammoniacal  solution  with  aluminium  amalgam.  After  filter- 
ing from  aluminium  hydroxide  and  concentrating  the  filtrate  to 
a  small  volume,  aminouracil  deposited  in  needles.  When  a 
solution  of  the  base  was  treated  with  picric  acid  we  obtained 
the  characteristic  picrate  of  aminouracil.  It  sintered  at  147° 
and  then  melted  at  247°,  with  effervescence.  Analysis  of  the 
free  base : 

Calculated  for 
C4H6OaN3.  Found. 

N  33-06  32.9 

Behavior  of  j-Nitrocytosine  when  Heated  with  a  Hydrochloric 
Acid  Solution  of  Nitrosyl  Chloride. — A  solution  of  nitrosyl 
chloride  was  prepared  according  to  the  directions  given  by 
Stanek.1  Three  grams  of  nitrocytosine  were  heated  in  a 
sealed  tube,  with  40  cc.  of  the  nitrosyl  chloride  solution,  for  4 
hours,  at  85°-95°.  It  was  then  allowed  to  stand  at  the  ordi- 
nary temperature  for  3  days.  A  clear  solution  resulted,  which 
slowly  evolved  nitrogen.  When  the  tube  was  opened  there 
was  considerable  pressure  and  a  crystalline  precipitate  was 
suspended  in  the  solution.  This  was  difficultly  soluble  in  hot 
water.  It  deposited,  on  cooling,  in  clusters  of  radiating  prisms. 
They  had  no  definite  melting  point  but  decomposed,  without 
melting,  when  heated  above  250°.  It  was  insoluble  in  acids, 
soluble  in  alkalies  and  did  not  respond  to  a  test  for  chlorine. 
A  nitrogen  determination  agreed  with  the  calculated  value  in 
nitrouracil  (Kjeldahl)  : 

Calculated  for 
C4H8O4N3.  Found. 

N  26.75  27.00 

1  Z.  physiol.  Chem.,  46,  265. 


1 68  Johnson,  Johns  and  Heyl. 

Action  of  Nitric  Acid  on  2-Ethylmercapto-^-brom-6-aminopy- 
rimidine. — This  mercaptobrornpyrimidine1  was  nitrated  under 
practically  the  same  conditions  as  were  employed  in  the  prepa- 
ration of  5-nitrocytosine  from  2-ethylmercapto-6-aminopyrimi- 
dine.  Eight  cc.  of  nitric  acid  (sp.  gr.  1.5)  were  mixed  with  4 
cc.  of  concentrated  sulphuric  acid.  Two  and  five-tenths 
grams  of  the  mercaptopyrimidine  were  then  slowly  added  to 
this  acid  mixture.  Much  heat  was  evolved  and  the  mercapto- 
pyrimidine dissolved  at  once,  but  the  reaction  was  not  as  vio- 
lent as  in  the  nitration  of  2-ethylmercapto-6-aminopyrimidine. 
After  standing  for  12  hours  the  solution  was  poured  upon 
crushed  ice  and  the  acids  neutralized  with  ammonia.  When 
the  liquid  was  concentrated  to  a  volume  of  25  cc.  and  cooled,  a 
microscopic  powder  deposited.  The  material  was  purified  by 
crystallization  from  hot  water.  It  decomposed,  without  melt- 
ing, when  heated  above  230°.  It  contained  bromine  but  did 
not  respond  to  a  test  for  sulphur.  A  nitrogen  determination 
agreed  with  the  calculated  value  in  5-bromcytosine  (Kjeldahl)  : 

Calculated  for 
C4H4ON3Br.  Found. 

N  22.10  22.17 

Action  of  Bromine  on  j-Nitrocytosine. — This  pyrimidine  was 
not  attacked  by  bromine.  It  was  suspended  in  glacial 
acetic  acid  and  treated  with  a  large  excess  of  bromine.  There 
was  no  apparent  change  after  standing  for  2  days.  More  bro- 
mine was  then  added  to  the  acetic  acid  and  the  solution  warmed 
in  a  water-bath.  Under  these  conditions  no  hydrobromic  acid 
was  evolved  and  the  nitrocytosine  was  recovered  unaltered. 

2-Oxy-5-nitro-6-phenylureapyrimidine, 
N CNHCONHC6H5 


io 

fc 


CNO2  . — Molecular    proportions    of  finely 


'H CH 

pulverized  5-nitrocytosine  and  phenylisocyanate  were  heated 
together,  at  100°,  for  several  hours.  The  reaction  was,  ap- 
parently, perfectly  smooth.  When  it  was  complete  the  urea 

1  Wheeler  and  Johnson  :  Loc.  cit. 


Researches  on  Pyrimidines.  169 

was  washed  with  alcohol,  to  remove  any  unaltered  phenyliso- 
cyanate  and  then  with  cold,  20  per  cent  hydrochloric  acid,  to 
remove  unaltered  nitrocytosine.  It  was  then  thoroughly 
washed  with  water  and  dried  at  100°.  It  was  practically  in- 
soluble in  all  solvents  and  slowly  decomposed,  without  melt- 
ing, when  heated  above  215°.  Analysis  (Kjeldahl)  : 

Calculated  for 
CiiH9O4N5.  Found. 

N  25.45  25.9 

Action  of  Acetic  Anhydride  on  Nitrocytosine. — 5-Nitrocytosine 
does  not  react  in  a  smooth  manner  with  acetic  anhydride. 
When  boiled  with  the  anhydride  it  slowly  dissolves  to  a  yel- 
low solution  that  assumes  a  red  color  on  prolonged  boiling. 
Different  products  are  formed  by  this  treatment  and  in  vary- 
ing proportions,  depending  upon  the  quantity  of  anhydride 
used  and  on  the  length  of  time  of  boiling.  In  every  experi- 
ment that  we  performed  we  invariably  obtained  mixtures  of  a 
monoacetyl  and  a  diacetyl  derivative,  with  unaltered  material. 
It  was  extremely  difficult  to  obtain  conditions  favorable  for  the 
formation  of  a  single  acetyl  compound. 

In  one  experiment  o.  5  gram  of  nitrocytosine  was  dissolved 
in  8  cc.  of  boiling  acetic  anhydride.  The  solution  was  then 
immediately  cooled,  when  we  obtained  a  deposit  of  lenticular 
shaped  crystals.  They  were  soluble  in  hot  water  and  deposi- 
ted, on  cooling,  in  prisms.  When  crystallized  a  second  time 
the  material  deposited  in  fern-like  forms  that  began  to  darken 
at  205°  and  decomposed  at  about  260°,  without  effervescence. 
Analysis  (Kjeldahl)  : 

Calculated  for 
C6H6O4N4.  Found. 

N  28.28  28.35 

In  two  other  experiments  we  duplicated  the  above  condi- 
tions, except  that  we  boiled  the  anhydride  solution  for  a  longer 
time.  We  obtained  material  that  deposited  from  water  in 
prismatic  crystals.  While  the  crystalline  form  suggested 
purity,  the  melting  points  were  unsatisfactory  and  the  nitro- 
gen determinations  indicated  that  we  were  dealing  with  a  mix- 
ture of  about  equal  proportions  of  a  monoacetyl  and  a  diacetyl 


170  Johnson,  Johns  and  Heyl. 

derivative.     The  material  that  was  analyzed  decomposed  at 
2o6°-2o8°,  with  effervescence. 

Calculated  for  Found. 

C«H504N4.       C8H806N4.  Average.  I.  II. 

N         28.28        23.33  25.8  26.0        25.81 

In  another  experiment  we  used  freshly  distilled  acetic  anhy- 
dride. One  and  seven-tenths  grams  of  the  nitropyrimidine  were 
suspended  in  10  cc.  of  the  anhydride  and  the  mixture  boiled  un- 
til the  pyrimidine  completely  dissolved.  Upon  cooling,  1.3 
grams  of  material  deposited.  It  was  difficultly  soluble  in  hot 
water  and  deposited,  on  cooling,  in  needle-like  prisms  that  de- 
composed at  273°-275°,  with  violent  effervescence.  A  nitro- 
gen determination  agreed  with  the  calculated  value  for  a  di- 
acetyl  derivative  : 

Calculated  for 
C8H8O6N4.  Found. 

N  23.33  23.23 

The  original  anhydride  filtrate  was  allowed  to  evaporate  to 
dryness.  We  obtained  a  crystalline  residue  that  proved  to  be 
a  mixture.  After  several  recrystallizations  from  water  we 
finally  isolated  a  product  that  possessed  all  the  properties  of 
the  original  5-nitrocytosine.  Analysis  (Kjeldahl)  : 

Calculated  for 
C4H4O3N4.  Found. 

N  35.89  35.3 

N=   =CNH3 

I             I 
2-Oxy-5)6-diaminopyrimidine,     CO        CNH2.  H2O. This 

I  II 

NH CH 

pyrimidine  was  formed  by  ^reducing  5-nitrocytosine  with 
aluminium  amalgam.  We  had  great  difficulty  in  preparing 
this  base  and  it  was  only  after  obtaining  negative  results  from 
several  experiments  that  we  eventually  found  conditions  under 
which  it  was  possible  to  isolate  it.  We  finally  succeeded  in  mak- 
ing the  compound  in  the  folio  wing  manner:  Three  grams  of  finely 
pulverized  5-nitrocytosine  were  suspended  in  cold  water,  in  con- 
tact with  aluminium  amalgam.  The  temperature  of  the  solution 
was  not  allowed  to  rise  above  35°  during  the  reduction,  and  the 


Researches  on  Pyrimidines.  171 

mixture  was  thoroughly  agitated  in  order  to  disintegrate  the 
coarser  particles  of  the  nitropyrimidine.  In  about  30  minutes 
the  nitropyrimidine  had  completely  dissolved  and  the  reduc- 
tion was  complete.  During  the  reduction  we  did  not  detect 
the  presence  of  ammonia,  but  after  the  reduction  was  finished 
it  was  noticeable,  indicating  a  partial  decomposition  of  the 
diamino  derivative.  In  order  to  avoid  decomposition  we 
quickly  filtered  from  aluminium  hydroxide,  when  we  obtained 
a  clear,  straw-colored  solution.  This  gradually  assumed  a 
dark  color  when  exposed  to  the  air.  In  order  to  isolate  the 
pyrimidine  base,  the  solution  was  concentrated  to  a  small  vol- 
ume by  slow  evaporation,  under  diminished  pressure.  The 
temperature  was  kept  below  50°  and  a  slow  stream  of  dry  hy- 
drogen was  passed  continually  through  the  capillary  tube  to 
avoid  oxidation.  Considerable  amorphous  material  deposited. 
After  concentrating  to  about  10  cc. ,  the  dark  colored  solution 
was  filtered  and  allowed  to  stand  in  an  ice  chest,  for  2 
days.  We  obtained  a  deposit  of  amorphous  substance  associa- 
ted with  clusters  of  radiating  prisms.  The  prisms  were  care- 
fully removed  and  washed  with  cold  water.  They  decomposed 
when  heated  above  230°  and  contained  water  of  crystallization. 
For  analysis  they  were  dried  in  the  atmosphere. 

The  water  of  crystallization  was  determined  by  heating  at 
I2o°-i3o°,  for  i  hour. 

0.1124  gram  substance  lost  0.0163  gram  HaO. 

Calculated  for 

C4H6ON4.H2O.  Found. 

N  12.50  14.50 

A  determination  of  nitrogen  in  the  anhydrous  material  gave 
the  following  result  (Kjeldahl). 

Calculated  for 

C4H6ON4.  Found. 

N  44.44  44.00 

This  base  was,  apparently,  quite  stable  after  drying  in  the 
air,  but  when  dissolved  in  water  it  slowly  decomposed  with 
separation  of  amorphous  material.  It  behaved  in  every  respect 
like  an  orthodiamine.  An  aqueous  solution  of  the  base  gave 
the  following  characteristic  reactions  :  Potassiobismuth  iodide 


172  Johnson,  Johns  and  Heyl. 

gave  an  insoluble,  red  precipitate ;  platinum  and  gold  chlor- 
ides were  reduced  to  metallic  platinum  and  gold  ;  Fehling's 
solution  was  reduced  at  once,  and  a  silver  mirror  was  formed 
when  a  solution  of  the  base  was  added  to  an  ammoniacal  solu- 
tion of  silver  nitrate. 

An  aqueous  solution  of  the  base  gave  an  alkaline  reaction 
when  tested  with  turmeric  and  litmus.  The  base  gave  no 
difficultly  soluble  salts  with  nitric,  hydrochloric  and  sulphuric 
acids.  It  was  precipitated  by  phosphotungstic  acid. 

The  Pier  ate  of  2-Oxy-^,6-diaminopyrimidine. — This  salt  de- 
posited from  hot  water  in  balls  of  microscopic  prisms.  The 
crystalline  form  resembled  very  much  that  of  uracil.  It  had 
no  definite  melting  point,  but  began  to  turn  brown  at  about 
170°,  slowly  decomposed  on  further  heating,  and  did  not  ef- 
fervesce at  300°.  Analysis  (Kjeldahl)  : 

Calculated  for  Found. 

C4H6ON4.C6H307N3.  I.  II. 

N  27.60  27.67  27.50 

The  Mercuric  Chloride  Salt. — This  was  obtained  when  mer- 
curic chloride  was  added  to  a  solution  of  the  base.  Analysis 
(Kjeldahl)  : 

Calculated  for 
C4H6ON4.HgCl2.  Found. 

N  14.1-  13.89 

2-Methylmercapto-4-oxy-5-nitros^-6-aminr>pyrimidine, 
N=:CNHa 

CHSSC          C  :  NOH.— Twenty-eight  grams  of  2-methylmer- 

II  I 

N CO 

capto-4-oxy-6-aminopyrimidine1  and  7.2  grams  of  sodium  hy- 
droxide were  dissolved  in  450  cc.  of  water.  To  this  solution 
was  added  a  concentrated  solution  of  14  grams  of  sodium  ni- 
trite and  then,  slowly,  24  grams  of  glacial  acetic  acid.  The 
mixture  was  allowed  to  stand  for  2  hours,  when  the  nitroso  de- 
rivative deposited  as  a  yellow,  crystalline  precipitate.  After 
thoroughly  washing  with  cold  water,  alcohol  and  ether  the 
crude  material  was  used  for  the  following  preparation  : 

1  Johnson  and  Johns  :  Loc.  cit. 


Researches  on  Pyrimidines.  173 

2-Methylmercapto-4-oxy-5,6-diaminopyrimidine, 
N CNH, 

II  II 

CH3SC  CNH2. — This  compound  was  prepared  by  redu- 

NH CO 

cing  the  above  nitroso  derivative  with  ammonium  sulphide. 
The  base  deposited  from  water  in  needle-like  prisms  that 
melted  at  2i5°-2i6°,  with  effervescence.  It  was  very  soluble 
in  alcohol.  It  was  unstable  and  gradually  assumed  a  red  color 
when  exposed  to  the  air.  Analysis  (Kjeldahl)  : 

Calculated  for 
C6H8ON4S.  Found. 

N  32.55  32.15 

2-Ethylmercapto-6-paratoluidinopyrimidine, 
N=   -CNHC6H4CH3 

C2H5SC          CH  . — This  compound  was  prepared 

'    II  II 

N CH 

by  dissolving  2-ethylmercapto-6-chlorpyrimidine  and  para- 
toluidine  in  dry  benzene,  in  the  proper  proportions,  and  warm- 
ing the  solution  for  several  hours  on  the  steam-bath.  The  ex- 
cess of  benzene  was  then  evaporated  on  the  steam-bath  and  the 
pyrimidine  purified  in  the  form  of  its  hydrochloride.  This 
deposited  from  dilute  hydrochloric  acid  in  needles  that  decom- 
posed at  i98°-2O7°,  with  effervescence.  The  salt  was  soluble 
in  hot  alcohol  and  deposited,  on  cooling,  in  needles.  Analysis 
(Kjeldahl)  : 

Calculated  for 

C13Hi6N3S.HCl.  Found. 

N  14.92  14.87 

The  free  base  was  obtained  when  the  hydrochloride  was 
treated  with  aqueous  ammonia.  It  separated  as  a  pasty  mass, 
which  finally  solidified.  It  deposited  from  petroleum  ether  in 
prismatic  crystals  that  melted,  at  104°,  to  a  clear  oil.  They 
were  extremely  soluble  in  alcohol  and  benzene.  Analysis 
(Kjeldahl)  : 


174  Johnson,  Johns  and  Heyl. 

Calculated  for 
Ci8H16N3S.  Found. 

N  17.14  16.93 

N=CNHC6H4CH3 

2-Oxy-6-paratoluidinopyrimidine,  CO        CH  ,  was 

I  II 

NH  -  CH 

obtained  in  the  form  of  its  hydrochloride  by  boiling  2-ethyl- 
mercapto-6-paratoluidinopyrimidine  with  concentrated  hydro- 
chloric acid  until  ethylmercaptan  ceased  to  be  evolved.  It  de- 
posited from  alcohol  in  microscopic  prisms  that  decomposed 
between  i8o°-i9o°,  with  effervescence.  It  was  soluble  in  hot 
water.  Analysis  (Kjeldahl)  : 

Calculated  for 

Found. 


N  17.68  17.81 

When  an  aqueous  solution  of  this  hydrochloric  acid  salt  was 
treated  with  ammonia  the  free  base  separated  as  a  crystalline 
precipitate.  It  was  insoluble  in  hot  water  and  the  ordinary 
organic  solvents,  but  was  purified  for  analysis  by  prolonged 
extraction  with  hot  water.  It  decomposed  slowly  when  heated 
above  280°  and  then  melted,  to  a  dark  colored  oil,  at  288°- 
289°,  with  violent  effervescence.  Analysis  (Kjeldahl)  : 

Calculated  for 
CnHnON3.  Found. 

N  20.89  20.71 

2-Ethylmercapto-6-orthotoluidinopyrimidine, 
N==CNHC6H4.CH$ 

C.H5SC          CH  .  -  From  2-ethylmercapto-6-chlor- 

II  II 

N  -  CH 

pyrimidine  and  orthotoluidine.  Its  hydrochloride  deposited 
from  dilute  hydrochloric  acid  in  granular  crystals  that  melted 
at  23o°-232°,  with  effervescence.  Analysis  (Kjeldahl)  : 

Calculated  for 
Ci3H16N3S.HCl.  Found. 

N  14.92  M-63 


Researches  on  Pyrimidines.  175 

When  an  aqueous  solution  of  the  hydrochloride  was  treated 
with  ammonia  the  base  separated  as  an  oil  which  solidified  on 
standing.  It  deposited  from  alcohol  in  prisms  that  melted,  at 
87°,  to  a  clear  oil.  Analysis  (Kjeldahl)  : 

Calculated  for 
Ci3H15N3S.  Found. 

N  17.14  l7-°4 

N—  CNHC8H4CH3 

2-Oxy-6-orthotoluidinopyrimidiney  CO        CH  ,was 

I  II 

NH  --  CH 

prepared  by  boiling  2-ethylmercapto-6-orthotoluidinopyrimidine 
with  hydrochloric  acid.  The  hydrochloride  was  very  soluble 
in  water  but  insoluble  in  benzene  and  acetone.  It  was  puri- 
fied for  analysis  by  crystallizing  from  95  per  cent  alcohol.  It 
deposited  in  lenticular  shaped  crystals  that  decomposed  at  227°- 
231°,  with  effervescence.  Analysis  (Kjeldahl)  : 

Calculated  for 
CUHUON8.HC1.  Found. 

N  17.68  17.35 

The  pyrimidine  base  was  insoluble  in  cold  water.  It  de- 
posited from  hot  water  in  radiating  prisms  that  decomposed  at 
262°.  Analysis  (Kjeldahl)  : 

Calculated  for 


Found. 

N  20.89  21.05 

2-Ethylmercapto-6-paraanisidinopyrimidine, 
N=CNHC6H46CH8 

C3H5SC          CH  .—From  2-ethylmercapto-6-chlor- 

II  II 

N  -  CH 

pyrimidine  and  paraanisidine.  The  hydrochloride  of  this  base 
deposited  from  hot  water  in  needles  that  melted  at  2Oo°-2Oi°, 
with  effervescence,  to  an  oil.  Analysis  (Kjeldahl)  : 

Calculated  for 
C13H16ON3S.HC1.  Pound. 

N  14.11  14.11 


176  Johnson,  Johns  and  Heyl. 

When  the  salt  was  treated  with  ammonia  the  base  was  ob- 
tained as  an  oil,  that  did  not  solidify  after  standing  for  several 
weeks. 

N=CNHC6H4OCH3 

2-Oxy-6-paraanisidinopyrimidine,  CO       CH  .  — 

I  II 

NH  -  CH 

The  hydrochloride  deposited  from  water  in  small,  radiating 
needles.  It  was  purified  for  analysis  by  recrystallizing  from 
alcohol  that  was  acidified  with  hydrochloric  acid.  It  decom- 
posed between  145°  and  165°,  with  effervescence.  Analysis 
(Kjeldahl)  : 

Calculated  for  Found. 

I.  II. 


N  16.56  16.72  16.65 

The  free  base  was  difficultly  soluble  in  all  ordinary  media 
and  showed  no  crystalline  form.  It  was  purified  for  analysis 
by  drying  at  110°,  for  2  hours.  It  melted  at  262°.  Analysis 
(Kjeldahl)  : 

Calculated  for  Found. 

CuHii02N3.  I.  II. 

N  19.35  19.68  19.53 

2'Ethylmercapto-6-metanitroanilinopyrimidiney 


-2H5SC 


Ni=CNHC6H4NO3 


C2H,SC          CH  .  —  From  2-ethylmercapto-6-chlor- 

II  II 

N CH 

pyrimidine  and  metanitroaniline.  In  this  experiment  we  ob- 
served that  the  free  base  could  be  more  easily  purified  than  its 
hydrochloric  acid  salt.  It  was  insoluble  in  water  and  soluble 
in  alcohol.  It  melted  at  175°.  Analysis  (Kjeldahl)  : 

Calculated  for  Found. 

C12H1202N4S.  I.  II. 

N  20.29  20-6  20.13 

The  hydrochloride  was  prepared  by  dissolving  the  base  in 
dilute  hydrochloric  acid.     It  deposited  in  needles  that  decom- 


Researches  on  Pyrimidines.  177 

posed  at  I4o°-i55°,  with  effervescence.     Analysis  (Kjeldahl): 

Calculated  for  Found. 

Ci2H12O2N4S.  HC1.  I.  II. 

N  17.92  17.5  17-67 

N CNHC6H4NO2 

2-Oxy-6-metanitroanilinopyrimidiney  CO        CH  . — 

I  II 

NH CH 

This  compound  could  not  be  obtained  in  the  usual  manner  by 
boiling  the  above  2-ethylmercapto-6-metanitroanilinopyrimi- 
dine  with  hydrochloric  acid.  The  mercaptopyrimidine  was 
recovered  unaltered  after  boiling  with  concentrated  hydro- 
chloric acid  for  15  hours.  In  order  to  remove  the  mercapto 
radical  it  was  necessary  to  boil  with  hydrobromic  acid.  The 
hydrobromide  was  purified  by  crystallization  from  95  per  cent 
alcohol.  It  decomposed  between  160°  and  180°,  with  effer- 
vescence. When  the  salt  was  treated  with  alcoholic  ammonia 
the  pyrimidine  base  separated  in  needle-like  prisms.  They 
decomposed  when  heated  above  275°.  Analysis  (Kjeldahl)  : 

Calculated  for 
C10H803N4.  Found. 

N  24.14  24.35 

NEW  HAVEN,  CONNM 
June  i,  1906. 


Reprinted  from  THE  JOURNAL  OF  BIOLOGICAL  CHEMISTRY,  1906,  ii,  pages  105-115 


III.     RESEARCHES  ON  PYRIMIDINS:     5-ETHYLCYTOSIN. 

(Eighteenth  Paper.) 

BY  TREAT  B.  JOHNSON  AND  GEORGE  A.  MENGE. 

(From  the  Sheffield  Laboratory  of  Yale  University.) 
(Received  for  publication,  May  13,  1906.) 

Methods  of  synthesizing  uracil,  I,  thymin,  II,  cytosin,  IV,  and 
5-methylcytosin,  V,  have  been  described  in  previous  papers 
from  this  laboratory.1 

Thymin,  II,  and  5-methylcytosin,  V,  are  the  simplest  mono- 
5-alkyl  derivatives  of  uracil,  I,  and  cytosin,  IV,  respectively. 
They  may  be  considered  as  the  second  members  of  two  homolo- 
gous series  of  which  uracil,  I,  and  cytosin,  IV,  are  the  primary 
substances. 

NH—  CO  NH—  CO  NH—  CO 

CO      CH     ->  CO      C.CH,     H>         CO      C.CH2CH3 

NH—  CH  NH—  CH  NH—  CH 

I  II  III 

N  =  CNH2  N  -  CNH,  N  =  CNH2 

CO     CH     ->  CO    C.CH3     ->          CO     C.CH,.CH3 

NH—  CH  NH—  CH  NH—  CH 

IV  V  VI 

The  work  described  in  this  paper  was  undertaken  with  the 
object  of  preparing  5-ethyluracil,  III,  and  5-ethylcytosin,  VI,  the 
third  homologues  of  these  two  series. 

We  find  that  ethylformate  condenses  with  normal  ethylbuty- 
rate  in  the  presence  of  sodium  ethylate,  or  metallic  sodium,  to 
form  the  sodium  salt  of  ethyl  formylbutyrate,  VII: 


CH3.CH2.CH2COOC2HS 

CH3.CH2.C:(CHONa)COOC,H,  +  C2H5OH 
VII 

When  this  sodium  salt,  VII,  was  dissolved  in  water  with  the 

»  Wheeler  and  Merriam,  Amer.  Chem.  Jour.,  xxix,  p.  478,  1903;  Wheeler 
and  Johnson,  ibid.,  xxix,  p.  492,  1903;  ibid,,  xxxi,  p.  591,  1904. 

105 


io6     Researches  on  Pyrimidins  :     5-Ethylcytosin 

calculated  quantity  of  pseudoethylthiourea  they  condensed  to 
form  2-ethylmercapto-5-ethyl-6-oxypyrimidin,  IX.  This  con- 
densation involves  the  intermediate  formation  of  a-eihyl-/3- 
pseudoethylthioureaacrylic  acid,  VIII.  We  have  succeeded  in 
isolating  this  compound. 

NH2    COOC2H$  NH2  COOH 

C2H5SC  +    CC2HS      -     C2HSSC       CC2H5  +NaOH-f  C2H5OH 

NH     CH.ONa  N  —  CH 

VIII 

NH2     COOH  NH—  CO 

C2HSSC         CC2H5      =        C2H5SC        CC2Hs  +  H2O 


IX 

Practically  a  quantitative  yield  of  5-ethyluracil,  III,  was  ob- 
tained when  this  mercaptopyrimidin,  IX,  was  boiled  with  hydro- 
bromic  acid: 

NH—  CO  NH—  CO 

C2H5SC        CC2HS  +  H2O  =         CO     C  C2HS  +  C2H5SH 

N  —  CH  NH—  CH 

IX  III 

When  2-ethylmercapto-5-ethyl-6-oxypyrimidin,  IX,  was 
heated  on  the  steam-bath  with  phosphorus  pentachloride  it  was 
converted  into  2-ethylmercapto-5-ethyl-6-chlorpyrimidin,  X: 

NH—  CO  N  =  CC1 

CjHjSC        CC2H5+PC15=      C2HSSC        CC2H$+POC13  +  HC1 

Jl-CH  A-CH 

X 

This  mercaptochlorpyrimidin,  X,  then  gave  a  quantitative 
yield  of  2-ethylmercapto-5-ethyl-6-aminopyrimidin,  XI,  when 
lieated  with  alcoholic  ammonia: 


N=CC1  N 

jSC      CC2H$  +  2NH,=  C2HSSC      CC2HS  +  NH4C1 

II      II  II       li 

N—  CH  N—  CH 

XI 

Finally   this    2-ethylmercapto-5-ethyl-6-aminopyrimidin,    XI 


Treat  B.  Johnson  and  George  A.  Menge        107 

was  converted  into  the  hydrobromide  of  5-ethylcytosin,  VI,  by 
boiling  with  hydrobromic  acid. 

N  =    CNH?  N  =  CNH, 

C2HSSC         CC2H$  +  HBr  +  H2O  =  C2HSSH  +     CO      CC2H,.HBr 

N  —  CH  NH— CH 

VI 

5-Ethylcytosin,  VI,  separates  from  water  without  water  of 
crystallization.  This  property  is  of  especial  interest.  Cytosin, 
IV,  and  5-methylcytosin,  V,  the  preceding  members  of  the  same 
series,  crystallize  with  one  molecule  and  a  half  molecule  of  water 
of  crystallization  respectively. 

C4H5ON3.H20,  C,H7ON3.*  H2p,  C6H9ON3. 

(Cytosin)  (5-Methylcytosin)       (5-Ethylcytosin) 

5-Ethylcytosin  is  more  soluble  in  water  than  cytosin,  and  less 
soluble  than  5-methylcytosin.  It  forms  normal  salts  (1:1)  with 
hydrochloric,  hydrobromic,  and  nitric  acids. 

One  of  the  most  characteristic  properties  of  5-methylcytosin 
was  its  tendency  to  form  basic  salts1  with  hydrobromic  and 
hydrochloric  acids.  We  now  find  that  5-ethylcytosin  likewise 
possesses  this  interesting  property.  When  ammonia  was  added 
to  an  aqueous  solution  of  the  hydrobromide  we  obtained  a 
mixture  of  two  hydrous,  basic  salts.  Our  analytical  determina- 
tions indicated  that  we  were  dealing  with  a  2:1,  XII,  and  a  3:1 
hydrobromide,  XIII.  On  account  of  the  small  amount  of  5- 
ethylcy  tosin  at  our  disposal  we  were  unable  to  make  as  thorough 
a  study  of  these  basic  salts  as  we  desired. 


(C6H9ON3)2 .  HBr.  H3O,  (CdH9ON3)3 .  HBr.  H,O. 

XII  XIII 

5-Ethylcytosin  is  precipitated  by  phosphotungstic  acid.  The- 
amino  radical  is  more  firmly  linked  in  this  base  than  in  cytosin 
and  5-methylcytosin.  While  the  latter  two  bases  are  converted 
into  uracil  and  thymin  when  heated  with  20  per  cent,  sulphuric 
acid,  5-ethylcytosin  was  recovered  unaltered  when  treated  under 
the  same  conditions. 

i  Wheeler  and  Johnson,  loc.  cit. 


o 

•< 

o 

s 

o    . 

ii 
I' 


O    H 


ffi  o 
**  fe 
a  o 


O     Q 
H     fc 


B 

if 


><   :2 

I" 

2  * 

lg 


*% 

js  13 

^  P. 


Solubili 
Water  a 


OJDOO 
HHBM 


. 

w      & 
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o-o  =o 


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is- 
lift 

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1 08 


Treat  B.  Johnson  and  George  A.  Menge        109 

EXPERIMENTAL    PART. 

Sodium  Salt  of  Ethyl  Formylbutyrate , 

C,HS.C:  (CHONa)COOC2Hs. 

This  salt  can  be  prepared  very  easily  by  proceeding  in  the 
following  manner:  A  known  weight  of  alcohol-free  sodium 
ethylate  was  suspended  in  dry  ether.  A  mixture  of  the  calcu- 
lated quantities  of  ethylformate  and  ethylbutyrate  was  then 
added  to  the  ether  and  the  condensation  allowed  to  proceed  at 
ordinary  temperature.  Sufficient  heat  was  evolved  to  cause  the 
ether  to  boil.  The  mixture  was  allowed  to  stand  for  four  days 
when  the  excess  of  ether  was  removed  by  sucking  a  current  of 
dry  air  through  the  solution.  We  obtained  a  thick  oil  which 
immediately  solidified  to  a  solid  cake  when  treated  with  a  little 
water.  No  further  purification  was  attempted.  This  salt  was- 
dissolved  in  cold  water  and  the  solution  washed  with  ether  to  re- 
move any  unaltered  esters.  This  solution  was  then  used  for 
the  condensations  described  in  this  paper.  In  our  calculations, 
we  have  assumed  that  the  sodium  salt  is  formed  in  practically 
theoretical  amount. 


NH-CO 

2-Ethylmercapto-$-ethyl-6-oxypyrimidm,    C2HSSC     CC2H, 

N-CH 

One  hundred  and  fifty  grams  of  normal  ethylbutyrate  were  con- 
densed with  ethylformate  in  presence  of  sodium  ethylate  as- 
described  in  the  preceding  experiment.  The  resulting  sodium 
salt  of  ethyl  formylbutyrate  was  then  dissolved  in  water,  and 
treated  with  an  aqueous  solution  of  0.5  molecular  proportion  of 
pseudoethylthiourea.  This  was  prepared  by  dissolving  119  grams 
of  the  hydrobromide  in  ice  water  and  neutralizing  the  hydro- 
bromic  acid  with  3  6  grams  of  potassium  hydroxide.  The  alkaline 
solution  was  allowed  to  stand  over  night  at  ordinary  temper- 
ature and  then  heated  on  the  steam-bath  for  about  two  hours. 
The  solution  was  then  filtered  and  acidified  with  acetic  acid. 
The  mercaptopyrimidin  separated  at  once  as  a  flocculent  pre- 
cipitate. After  drying  over  sulphuric  acid  the  crude  material 
weighed  40  grams,  corresponding  to  38  per  cent,  of  the  theoretical,. 


1  10     Researches  on  Pyrimidins  :     5-Ethylcytosin 

calculating  from  the  weight  of  pseudourea  used.  It  was  ex- 
tremely soluble  in  alcohol  and  benzene,  and  moderately  soluble  in 
ether.  It  was  difficultly  soluble  in  water.  It  deposited  from  hot 
water  or  dilute  alcohol  in  well  developed  prisms  that  melted  at 
1  1  9-1  20°  C.  to  a  clear  oil.  Analysis  (Kjeldahl): 

Calculated  for  C8H,2ONaS:  Found: 

N  -15  .  17  per  cent.  15  .  12  per  cent. 

a-Ethyl-p-pseudoethylihioureaacrylic  acid  , 

H2N(C2HSS):N.CH:C(C2HS).COOH. 

This  was  obtained  as  an  intermediate  product  in  the  preceding 
condensation.  After  filtering  from  the  2-ethylmercapto-5-ethyl- 
6-oxypyrimidin  the  acetic  acid  filtrate  was  concentrated  on  the 
steam-bath  and  then  allowed  to  stand  at  ordinary  temperature 
for  several  hours.  A  heavy,  flocculent  precipitate  separated  on 
cooling.  The  substance  was  very  soluble  in  alcohol.  When 
heated  above  its  decomposition  point  it  was  converted  into  the 
mercaptopyrimidin  above.  It  deposited  from  hot  alcohol  in 
plates  that  melted  at  148°—  149°  C.,  with  effervescence,  to  a  clear 
oil.  When  this  oil  was  allowed  to  cool  below  100°  C.  it  solidified. 
Upon  heating  again  in  the  capillary  tube  it  melted  at  117°-!  18°  C. 
to  a  clear  oil.  Analysis  (Kjeldahl): 

Calculated  for  C8H,4O2N2S:  Found: 

N  -13.86  per  cent.  13  .70  per  cent. 

N-  CC1 
2-Ethylmercapto-$-ethyl-6-chlorpyrimidin,  C2H$SC      CC2HS 


Twenty-five  grams  of  2-ethylmercapto-5-ethyl-6-oxypyrimidin 
and  a  slight  excess  over  one  molecular  proportion  of  phosphorus 
pentachloride  were  mixed  in  a  flask  and  gently  heated  on  the 
steam-bath.  A  violent  reaction  took  place  with  evolution  of 
hydrochloric  acid  gas.  We  obtained  a  dark  colored  liquid  that 
was  heated  for  several  minutes  at  100°  C.  to  complete  the 
reaction.  The  liquid  was  then  poured  upon  crushed  ice  to  de- 
compose the  phosphorus  halides.  The  chlorpyrimidin  was  ex- 
tracted with  ether,  dried  over  calcium  chloride,  and  purified  by 
distillation  under  diminished  pressure.  It  boiled  at  i6o°-i63°  G. 


Treat  B.  Johnson  and  George  A.  Menge        in 

under  24  mm.  pressure.  It  would  not  solidify  in  a  freezing 
mixture.  The  yield  of  pure  distilled  material  was  14  grams,  or 
about  54  per  cent,  of  the  theoretical.  When  boiled  with  water  it 
was  converted  into  the  original  2-ethylmercapto-5-ethyl-6-oxy- 
P3'rimidin.  Analysis  (Kjeldahl): 

Calculated   for  C,HUN2SC1:  Found: 

N  -=13  8  per  cent.  13-43  per  cent. 

N=CNH2 

2-Ethylmercapto-$-ethyl-6-ammopyrimidin,    C2H5SC     CC2HS 

N-  CH 

This  aminopyrimidin  was  obtained  when  the  chlorpyrimidin 
above  was  heated  in  a  sealed  tube  with  alcoholic  ammonia  at 
130°— 140°  C.  for  two  hours.  The  excess  of  ammonia  and  alcohol 
was  then  removed  by  evaporation  on  the  steam-bath.  The 
residue  was  then  treated  with  water  to  remove  ammonium 
chloride.  We  obtained  an  oil  that  was  very  soluble  in  ether. 
When  the  ether  solution  was  allowed  to  evaporate  spontaneously 
the  aminopyrimidin  deposited  in  prismatic  crystals.  It  was 
insoluble  in  ligroin  but  extremely  soluble  in  benzene.  It  deposited 
from  a  mixture  of  these  two  solvents  in  stout  prisms  that 
melted  at  74°-76°  C.  to  an  oil.  Analysis  (Kjeldahl): 

Calculated  for  C8H13N3S:  Found: 

N=22.95  per  cent.  22.88  per  cent 

NH-CO 

2,  6-Dioxy-$-ethylpyrimidin  ($-Ethyluracil) ,     co      CC2H$ 

NH-CH 

This  pyrimidin  was  prepared  by  boiling  2-ethylmercapto-5- 
ethyl-6-oxypyrimidin  with  hydrobromic  acid.  It  was  difficultly 
soluble  in  water.  One  part  of  the  pyrimidin  dissolved  in  about 
625  parts  of  water  at  25°  C.  It  deposited  from  hot  water  in  balls 
of  microscopic  prisms  that  melted  at  about  300°  C.  with  decom- 
position. Analysis  (Kjeldahl): 

Calculated  for  C6H8O2N2 :  Found: 

N=2o.o  per  cent  19.8  per  cent. 


H2     Researches  on  Pyrimidins  :     5-Ethylcytosin 

$-Eihylcytosin  Monohydrobromide  (Anhydrous). 

This  salt  was  obtained  when  2-ethylmercapto-5-ethyl-6-amino- 
pyrimidin  was  boiled  with  hydrobromic  acid.  When  the  acid 
solution  was  allowed  to  stand,  the  hydrobromide  deposited  in 
large  prisms.  They  did  not  contain  water  of  crystallization. 
When  heated  in  a  capillary  tube  the  salt  began  to  darken  at  about 
265°  and  melted  at  284°-286°  C.  with  effervescence.  Analysis 
(Kjeldahl): 

Calculated  for  C6H9ON3.HBr:  Found: 

N=i9.i3  per  cent.  19.2  per  cent. 

N    =  CNH2 

2-Oxy-$-ethyl-6-aminopyrimidin  ($-Ethylcytosiri) ,  co      CCZHS 

NH— CH 

In  order  to  obtain  this  base,  the  monohydrobromide,  described 
above,  was  dissolved  in  water;  the  bromide  was  removed  by 
means  of  silver  sulphate;  the  excess  of  silver  was  precipitated 
with  hydrogen  sulphide,  the  sulphuric  acid  by  barium  hydroxide, 
and  then  the  excess  of  barium  with  carbon  dioxide.  The  clear 
solution  was  then  concentrated  to  a  small  volume,  whereupon 
on  cooling  the  base  deposited  in  beautiful,  slender  prisms.  They 
did  not  contain  water  of  crystallization.  One  part  of  the  base 
dissolved  in  about  75  parts  of  water  at  25°  C.  When  heated  in  a 
capillary  tube  it  melted  with  effervescence  at  282°-283°  C. 
Analysis  (Kjeldahl): 

Calculated   for  C«H9ON3:  Found: 

N  =30.21  per  cent.  30.03  per  cent. 

The  base  was  precipitated  from  its  aqueous  solution  by 
mercuric  chloride  and  phosphotungstic  acid.  The  phospho- 
tungstate  was  soluble  in  boiling  water  and  deposited  again  on 
cooling.  When  a  solution  of  the  pyrimidin  base  was  treated  with 
a  solution  of  potassio-bismuth  iodide  a  red  precipitate  was  ob- 
tained. It  was  insoluble  in  hot  water. 

5-Ethylcytosin  was  heated  with  20  per  cent,  sulphuric  acid  for 
six  hours  at  i4o°-i5o°C.  When  the  pressure  tube  was  exam- 
ined there  was  no  apparent  decomposition.  Upon  concentrating 
on  the  steam-bath  we  did  not  obtain  a  deposit  of  5-ethyluracil. 
The  sulphuric  acid  was  removed  with  barium  hydroxide,  and  the 


Treat  B.  Johnson  and  George  A.  Menge       113 

excess  of  alkali  with  carbon  dioxide.  When  the  neutral  solution 
was  concentrated  to  a  small  volume,  the  unaltered  base  deposited 
in  characteristic,  slender  prisms  that  melted  at  282°-283°C. 
with  effervescence.  When  mixed  with  the  original  base  the 
melting-point  was  not  lowered. 

Platinum  Chloride  Double  Salt. 

This  salt  was  extremely  soluble  in  water.  It  deposited  from 
hot  water  in  radiating,  transparent  prisms.  A  nitrogen  deter- 
mination gave  the  following  result: 

Calculated  for  (C6H9ON3)2.H2PtCl6.2HaO:  Found: 

N— 11.62  per  cent.  11.56  per  cent 

The  Pier  ate  of  $-Ethylcytosin. 

This  salt  was  prepared  by  treating  a  solution  of  the  base  with 
picric  acid.  It  was  difficultly  soluble  in  water.  It  deposited 
from  hot  water  in  yellow,  opaque  crystals.  When  heated  in  a 
capillary  tube  they  decomposed  at  277°-278°C. 

$-Ethylcytosin  Monohydrochloride  (Anhydrous). 

This  salt  was  prepared  by  dissolving  5-ethylcytosin  in  dilute 
hydrochloric  acid  and  allowing  the  solution  to  slowly  evaporate 
in  a  desiccator  over  sulphuric  acid.  It  deposited  in  flat  prisms. 
They  were  extremely  soluble  in  cold  water  and  melted  at  238°- 
240°  C.  with  slight  effervescence.  Analysis  (Kjeldahl): 

Calculated  for  C6H9ON3 .  HC1 :  Found : 

N-23-93  per  cent.  23.90  per  cent. 

Nitrate  of  $-Ethylcytosin. 

Obtained  by  allowing  a  nitric  acid  solution  of  the  base  to 
slowly  evaporate  in  a  desiccator  over  sulphuric  acid.  It  de- 
posited in  stout  prisms.  They  decomposed  at  about  1 70°-! 7 2°  C. 
The  salt  was  very  soluble  in  cold  water.  Analysis  (Kjeldahl) : 

Calculated  for  C6H9ON3.HNO3:  Found: 

N— 27.72  per  cent.  27-39  P6*"  cent. 

Basic  Hydrobromides  of  $-Ethylcytosin. 

Some  of  the  2-ethylmercapto-5-ethyl-6-aminopyrimidin  was 
boiled  with  hydrobromic  acid  until  ethyl  mercaptan  ceased  to  be 
evolved.  The  solution  was  then  evaporated  to  dry  ness  to  remove 
the  excess  of  acid.  Upon  adding  ammonia  to  an  aqueous  solution 


H4       Researches  on  Pyrimidins  :  5-Ethylcytosin 

of  the  hydrobromide  we  obtained  an  immediate  precipitate  in  the 
form  of  well  developed  prisms.  This  precipitate  was'difficultly 
soluble  in  water.  It  deposited  from  hot  water  in  clusters  of 
radiating  prisms  associated  with  diamond-shaped  crystals. 
They  decomposed  at  258°-26o°  C.  with  violent  effervescence. 
We  were  unable  to  raise  this  decomposition  point  by  repeated 
recrystallizations  from  hot  water.  The  material  gave  a  strong 
test  for  bromine.  The  analytical  determinations  indicated  that 
we  were  not  dealing  with  a  homogeneous  salt,  but  a  mixture  of 
two  hydrous,  basic  salts.  Our  determinations  agreed  with  the 
calculated  values  for  a  mixture  of  about  equal  proportions  of  a 
2:1  and  a  3:1  hydrobromide. 

0.3358  gram  of  substance  lost  0.0127  gram  on  heating  to  constant 
weight  at  ioo°-iio°  C. 
For  (C6H9ON3)2.HBr.H2O— 

Calculated:  H2O    =4.8  per  cent. 
For  (C6H9ON3)3HBr.H2O— 

Calculated:  H2O  =  3.4  per  cent. 
Average:  H2O  —  4.1  per  cent. 

Found:  H2O    -  3.78  per  cent. 

Nitrogen  determinations  in  the  hydrous  material  (Kjeldahl) : 
For  (C6H9ON3)2.HBr.H2O— 

Calculated  :  N    =22.31  per  cent. 
For  (C6H9ON3)3.HBr.H2O— 

Calculated:  N=  24.41  per  cent. 
Average  :  N    =23.36  per  cent. 

Found  :  N   —  (i)  23.29;  (2)  23.31  per  cent. 
Nitrogen  determinations  in  the  anhydrous  material  (Kjeldahl) : 
For  (C6H9ONj)a.HBr— 

Calculated  :  N    =23.39  per  cent. 
For  (C,H9ON3)3.HBr— 

Calculated  :  N  =»  25  .30  per  cent. 
Average  :  N  =24.34  per  cent. 
Found  :  N  =  (i)  24.48;  (2)  24.07  per  cent. 

N  =  CC1 
2, 6-Dichlorpyrimidin,  C1C  CH 

N  —  CH 
This  compound  has  been  described  by  Gabriel.1  He  prepared 

iBer,  d.  deutsch.  chem.  Gesellsch.,  xxxviii,  p.  1690,  1905. 


Treat  B.  Johnson  and  George  A.  Menge       115 

it  by  heating  uracil  with  phosphorus  oxy chloride  at  140°  C.  He 
states  that  it  melted  at  61°  C.  and  boiled  at  2o8.5°-209.5  °  C. 
at  773  mm.  We  had  prepared  the  same  chloride,  previous  to 
this  publication,  by  warming  2-thiouracil1  on  the  steam-bath 
with  phosphorus  pentachloride.  From  35  grams  of  2-thiouracil 
we  obtained  19.2  grams  of  the  dichlorpyrimidin  boiling  at 
101°  C.  at  23  mm.  In  another  experiment  we  obtained  13  grams 
from  20  grams  of  2-thiouracil.  It  boiled  at  198°  C.  at  760  mm. 
Our  compound  melted  at  63°  C.  to  a  clear  oil.  It  was  soluble 
in  alcohol,  benzene,  and  ether.  Its  vapors  attacked  the  eyes. 
Analysis  (Kjeldahl): 

Calculated  for  C4H2NjCl,;  Found: 

N  —  18.79  Per  cent.  18.78  per  cent. 

» Wheeler  and  Bristol,  Amer.    Ghent.  Jour,  xxxiii,  p.  458,  1905. 


[Reprinted  from  the  American  Chemical  Journal,  Vol.  XXXVII.    No.  4. 
April,  1907.] 


Contributions  from  the  Sheffield  Laboratory  of  Yale  University. 

CXLII.—  RESEARCHES  ON  PYRIMIDINES:   SYNTHESIS 
OF  URACIL-5-CARBOXYUC  ACID. 

[NINETEENTH  PAPER.] 

BY  HENRY  I,.  WHEELER,  TREAT  B.  JOHNSON,  AND  CARL  O.  JOHNS. 

A  new  substance,  having  acid  properties,  called  orotic  acid 
(Acido  orotico)  has  been  isolated  by  Biscaro  and  Belloni1 
from  milk.  They  assign  to  this  compound  the  empirical 
formula,  C5H4O4N2.H2O,  and  believe  that  its  structure  is  to 
be  represented  by  one  of  the  following  formulas: 


NH.CH2.CO  /NH  .CO  .CH 

| 
NH  .  CO.CO 


OC  |      . 

\NH.  CO  .CO 


1  Annuario  della  Soc.  Chimica  di  Milano,  XI,  fasc.  I  (1905);  /dzYf.,XI,  fasc.  II  (1905) 
Vide  also  Centrabl.,  1905,  I,  63,  64.  We  take  this  occasion  to  thank  the  above  authors 
for  sending  us  reprints  of  these  two  articles. 


Researches  on  Pyrimidines.  393 

It  seemed  to  us  that  instead  of  a  ring  with  7  members,  one 
with  5  or  6  would  most  probably  prove  to  be  correct.  The 
properties  of  the  substance  and  the  fact  that  it  gives  urea 
on  oxidation,  suggested  that  it  might  be  a  pyrimidine. 

The  above  empirical  formula  is  that  of  a  uracil  carboxylic 
acid  having  a  molecule  of  water  of  crystallization.  There 
are  2  uracil  carboxylic  acids  which  have  the  acid  group  at- 
tached to  carbon,  namely,  the  4-  (I.)  and  5-  (II.)  derivatives, 

HN— CO  HN— CO 

I  I       I 

CH         ,  OC    CCOOH. 

I      II  I      II 

HN— CCOOH  HN— CH 

I.  II. 

As  neither  of  these  acids  have  hitherto  been  prepared,  a  de- 
scription is  now  given  of  the  preparation  and  properties  of  the 
latter  acid,  while  an  account  of  uracil-4-carboxylic  acid  will 
appear  in  a  later  article.  The  study  of  these  acids,  and  also 
the  carboxyl  derivatives  of  thymine  and  cytosine,  is  of  in- 
terest on  account  of  the  possibility  that  in  the  nucleic  acids 
uracil,  thymine  and  cytosine  may  exist  as  carboxyl  deriva- 
tives, being  held  together  not  alone  by  means  of  phosphorus 
atoms,  as  suggested  by  Bang1  and  Osborne  and  Harris,2  but 
also  by  an  acid  amide  or  polypeptide  grouping  as  in  the  case  of 
the  proteids.  In  such  an  event  the  means  hitherto  used  to  dis- 
rupt the  nucleic  acid  molecule  must  also  cause  a  loss  of  the 
carboxyl  group  from  the  pyrimidines.  In  this  connection 
it  is  interesting  to  note  that  uracil-4-carboxylic  acid  can  be 
heated  with  20  per  cent  sulphuric  acid,  at  i6o°-i  70°,  without 
alteration  while,  by  such  treatment,  uracil- 5 -carboxylic  acid 
is  quantitatively  converted  into  uracil.  In  fact,  simply  on 
prolonged  boiling  of  this  acid  with  hydrochloric  acid  it  is  con- 
verted into  uracil.  Uracil  may,  therefore,  exist  in  the  nucleic 
acids  as  a  5-carboxyl  compound.  We  have  shown  that  the 
pseudothioureas,  H2NC(SR)  :  NH,  will  react  with  aldehyde3 

1  Z.  physiol.  Chem.,  31,  425  (1900). 

2  Conn.  Exper.  Sta.  Rep.,  1901,  p.  418. 

3  THIS  JOURNAL,  29,  480  (1903). 


394  Wheeler,  Johnson  and  Johns. 

and  ketone  esters  to  form  pyrimidines  in  cases  where  urea  re- 
fuses to  act.  According  to  Behrend  the  alkyl  acetoacetic 
esters  do  not  condense  with  urea.1  We  found  that  the  methyl 
and  ethyl  derivatives  give  pyrimidines  with  the  pseudothio- 
ureas.  In  that  article  we  described  4,5-dimethyluracil  as  new, 
having  missed  the  fact  that  Schlenker  had  obtained  this  sub- 
stance by  a  different  method.2 

Another  striking  example  of  the  difference  between  urea 
and  a  pseudothiourea  was  found  when  we  tried  the  behavior 
of  Claisen's  ethoxymethylenemalonic  ester3  toward  these 
compounds.  Urea  showed  no  sign  of  reacting  at  140°  and  a 
condensation  was  not  effected  on  standing  in  alkaline  solu- 
tions. 

On  the  other  hand,  when  ethoxymethylenemalonic  ester  was 
added  to  an  alkaline,  aqueous  solution  of  ethylpseudothiourea 
hydrobromide,4  an  immediate  reaction  took  place  and  a  salt 
of  2-ethylmercapto-5-carbethoxy-6-oxypyrimidine  separated. 
This  condensation  can  be  represented  as  follows : 

HNH     C2H5OCO  HN— CO  C2H5OH 

i 


CC( 


C2H5SC    +  CC02C2H5==C2H5SC    CCO2C2H5  + 

II  II  II      II 

NH     C2H5OCH  N— CH  C2H6OH 

2-Kthylmercapto-5-carbethoxy-6-oxypyrimidine  (I.  see  be- 
low) can  be  converted  directly  into  uracil-5-carboxylic  acid 
(IV.)  by  simply  boiling  with  aqueous  hydrochloric  acid.  When 
the  mercapto  ester  (I.)  is  boiled,  in  alcoholic  solution,  with  a 
small  quantity  of  hydrochloric  acid,  uracil-5-ethylcarboxylate 
(II.)  results.  And  this,  on  saponification,  gives  uracil-5- 
carboxylic  acid.  On  the  other  hand,  warm  alkalies  saponify 
the  mercapto  ester  (I.)  and  give  2-ethylmercapto-5-carboxyl- 
6-oxypyrimidine  (III.),  which,  with  hot  hydrochloric  acid, 
gives  uracil-5-carboxylic  acid  (IV.).  When  the  acid  (IV.) 
is  melted  it  gives  uracil  (VI.). 

1  Ann.  Chem.  (Uebig),  229,  16  (1885). 

2  Ber.  d.  chem.  Ges.,  34,  2812  (1901). 

a  Ann.  Chem.  (I,iebig),  297,  75  (1897). 
4  THIS  JOURNAL,  29,  483  (1903). 


Researches  on  Pyrimidines. 


395 


The  formation  of  uracil,  in  this  manner  and  also  on  heating 
with  acids,  shows  that  the  condensation  took  place  as  repre- 
sented in  the  above  equation  and  that  the  product  (I.)  is  not  a 
barbituric  acid  derivative.  In  fact,  we  have  not  yet  observed 
a  satisfactory  condensation  of  malonic  ester,  or  any  of  its 
derivatives,  with  the  pseudothioureas  to  form  barbituric 
acid  derivatives.  The  substance  represented  by  Formula 
V.,  uramidomethylenmalonic  ester,  was  occasionally  found 
as  a  by-product  in  the  mother  liquors  of  the  condensation. 
On  saponification  it  gave  uracil- 5 -carboxy lie  acid.  These 
compounds  and  their  transformations  can  be  represented 
as  follows: 


HN—  CO 

6SC 


HN— CO  HNH  COOC2H6 

C 


C2H6SC    CC02C2H6*^C2H5SC    CCO2H      OC       CCO2C2H6 


N—  CH 


N— CH 
III. 


HN— CH 
V. 


HN—  CO 

OC    CC02C2H5 

I       II 
HN—  CH 

II. 


HN-CO 

OC     CCO2H 

I      II 
HN— CH 

IV. 


HN— CO 

OC     CH 

I      II 
HN— CH 

VI. 


In  some  respects  the  properties  of  uracil-5-carboxylic  acid 
agree  closely  with  those  of  orotic  acid.  It  is  difficultly  solu- 
in  water,  difficultly  or  insoluble  in  organic  solvents  and  it  crys- 
tallizes with  the  required  i  molecule  of  water  of  crystalliza- 
tion. Orotic  acid  is  said  to  decompose  at  260°.  Our  acid 
melts,  with  decomposition,  at  278°.  The  potassium  salt  that 
crystallizes  from  solutions  containing  an  excess  of  alkali  is 
a  monopotassium  salt,  C5H3O4N2K.  Like  orotic  acid,  our 
acid  is  dibasic  and  forms  2  series  of  salts.  The  potassium 
salt  gives  precipitates  with  barium  chloride  (crystalline), 
lead  acetate  and  silver  nitrate. 

On   the   other   hand,   uracil-5-carboxylic   acid   differs  from 


396  Wheeler,  Johnson  and  Johns. 

orotic  acid  as  follows:  It  does  not  give  a  monosilver  salt  hav- 
ing the  composition  C5H3O4N2Ag.H2O,  which  Biscaro  and 
Belloni  state  is  formed  when  silver  nitrate  is  added  to  a  solu- 
tion of  the  monopotassium  salt.  In  our  case,  when  the  mono- 
potassium  salt  or  alkali,  acid  and  silver  nitrate,  in  the  pro- 
portion i :  i :  i  were  used,  the  silver  salt  formed  was  a  disilver 
salt,  a  corresponding  amount  of  acid  remaining  in  the  filtrate. 

When  methyl  iodide  was  allowed  to  react,  under  pressure, 
on  either  mono  or  disilver  orotate,  Biscaro  and  Belloni  obtained 
a  monomethyl  derivative  melting  at  248°-25o°.  When  we 
heated  our  silver  salt  with  methyl  iodide,  in  a  closed  tube 
at  100°,  we  obtained  a  mixture  of  substances  from  which  a 
dimethyl  derivative,  melting  about  254°-256°,  was  isolated. 
Their  monoethyl  ester  melted  at  200°;  our  product,  obtained 
in  like  manner  from  the  silver  salt,  melted  at  i62°-i63,  and 
the  analysis  showed  that  it  was  a  diethyl  derivative. 

The  free  uracil-5-carboxylic  acid  does  not  give  a  precipi- 
tate with  barium  chloride,  and  we  were  unable  to  obtain  a  di- 
chloride,  which  could  be  crystallized  from  boiling  water  with- 
out reverting  to  the  acid,  when  the  potassium  salt  was  heated 
with  phosphorus  oxychloride. 

EXPERIMENTAL   PART. 

2-Ethylmercapto-5-carbethoxy-6-oxypyrimidine, 
HN CO 


CC02C2H5.— 


C2H5SC          CCO2C2H5.— The    best    results    in    the    prepara- 

N CH 

tion  of  this  substance  were  obtained  as  follows:  Fifty-four 
grams  of  ethoxymethylenemalonic  ester  were  added  to  a  solu- 
tion of  50  grams  of  ethylpseudothiourea  hydrobromide  in  50 
cc.  of  water.  To  this  mixture  30  grams  of  potassium  hydrox- 
ide were  slowly  added  and  the  solution  was  kept  cold.  The 
addition  of  alkali  produced  a  yellow  color  and  the  solution 
became  semisolid  from  the  separation  of  a  bulky,  yellow 
precipitate.  This  impure  potassium  salt,  when  dry,  weighed 
58  grams,  the  yield  being  87  per  cent  of  the  calculated,  theory 


Researches  on  Pyrimidines.  397 

requiring  66.5  grams.     It  crystallized  from  water  in  the  form 
of  colorless  prisms  and  from  alcohol  in  needles. 

When  a  strong  aqueous  solution  of  the  potassium  salt  was 
treated  with  dilute  hydrochloric  acid,  avoiding  an  excess  of  acid, 
2-ethylmercapto-5-carbethoxy-6-oxypyrimidine  separated  as 
a  white,  crystalline  precipitate.  This  substance  is  readily 
soluble  in  hot  alcohol  and  it  separates  in  the  form  of  long, 
slender,  colorless  prisms;  from  water  it  forms  long,  bulky, 
asbestos-like  needles.  It  melts  at  131°  to  a  clear  oil  and  it 
gave  the  following  results  on  analysis  (Kjeldahl) : 

Calculated  for  Found. 

C9Hi2O8N2S.  I.  II. 

N  12.23  12.02  12.28 

This  ester  dissolves  in  cold  hydrochloric  acid  and  is  repre- 
cipitated  by  ammonia.  It  has  both  acid  and  basic  proper- 
ties. 

Uramidomethylenemalonic  Ester,  H2NCONHCH  :  C(CO2C2H5)2. 
— This  substance  was  obtained,  in  2  experiments,  by  pre- 
cipitating with  hydrochloric  acid,  the  filtrate  from  which  the 
potassium  salt  of  2-ethylmercapto-5-carbethoxy-6-oxypyrimidine 
had  separated.  In  the  above  case  the  amount  obtained  was 
4.8  grams.  It  is  very  difficultly  soluble  in  boiling  water,  readily 
soluble  in  hot  alcohol;  when  crystallized  from  50  per  cent 
alcohol  it  forms  bunches  of  colorless  prisms  melting  at  206°, 
with  effervescence.  Nitrogen  determinations  gave  (Kjeldahl) : 

Calculated  for  Found. 

C9H1406N2.  I.  II. 

N  12.17  12.22  12. O6 

This  material  has  acid  properties.  When  warmed  with 
alkali,  saponification  takes  place  and  hydrochloric  acid  then 
precipitates  uracil-5-carboxylic  acid. 

2-Ethylmercapto-5-carboxyl-6-oxypyrimidine, 
HN CO 

I  I 

C2H5SC          CCO2H.— Ten    grams   of   the    potassium  salt    of 

II  II 
N CH 

2-ethylmercapto-5-carbethoxy-6-oxypyrimidme  were   dissolved 


398  Wheeler,  Johnson  and  Johns. 

in  hot  alcohol  and  a  hot  solution  of  4.3  grams  of  potassium 
hydroxide,  in  a  little  water,  were  added.  Saponification  took 
place  immediately  and  the  solution  became  a  thick  jelly.  The 
alcohol  was  then  evaporated  and  the  residue  taken  up  in  a  little 
water.  On  adding  an  excess  of  hydrochloric  acid  a  white 
precipitate  of  the  mercapto  acid  separated.  It  weighed  7.1 
grams,  while  the  calculated  is  7.5  grams,  the  yield  being  94.6 
per  cent  of  theory. 

This  acid  dissolves  readily  in  hot  alcohol,  less  readily  in  hot 
water,  from  which  solvent  it  forms  bunches  of  colorless,  sharp- 
cornered  plates.  It  melts  to  a  clear  oil  at  167°  and  effer- 
vesces at  a  higher  temperature.  Nitrogen  determination: 

Calculated  for 
C7H803N2S.  Found. 

N  14-00  13.72 

This  acid  appears  to  be  stronger  than  acetic  acid, 
since  it  was  not  liberated  from  its  potassium  salt  by  means 
of  an  excess  of  acetic  acid.  It  gives  a  bulky,  white,  gelatinous 
precipitate  with  alkali  and  silver  nitrate.  When  warmed 
with  hydrochloric  acid,  it  readily  evolves  mercaptan  and  gives 
uracil-5-carboxylic  acid. 

HN CO 

I             I 
Uracil-5-ethykarboxylate,  OC  CCO^Hg. Ten    grams 

HN CH 

of  the  potassium  salt  of  2-ethylmercapto-5-carbethoxy— 6 
oxypyrimidine  were  dissolved,  or  suspended,  in  about  75  cc. 
of  strong  alcohol,  and  about  5  cc.  of  concentrated  hydrochloric 
acid  were  added.  The  whole  was  then  boiled  with  a  return 
condenser  for  several  hours;  the  alcohol  was  evaporated  and 
the  residue  was  taken  up  in  about  60  cc.  of  warm  water.  The 
hydrochloric  acid  was  neutralized  with  ammonia  and  the 
solution  was  then  filtered  hot.  On  adding  an  excess  of  strong 
ammonia  to  the  filtrate  the  ammonium  salt  of  uracil- 5 -ethyl- 
carboxylate  separated  as  a  sponge-like  mass  of  long,  slender, 
colorless  needles.  This  was  dissolved  in  about  50  cc.  of  water  by 
warming  and  then  a  slight  excess  of  acetic  acid  was  added. 


Researches  on  Pyrimidines.  399 

On  cooling,  a  granular,  crystalline  precipitate  of  the  free  ester 
separated.  This  was  found  to  be  very  soluble  in  hot  water 
and  moderately  so  in  cold.  It  was  difficultly  soluble  in  alco- 
hol. When  crystallized  from  water  it  formed  flat,  sharp- 
pointed  prisms,  melting  at  236°-237°.  Analysis: 

Calculated  for  Found. 

C7H804N2.  I.  II. 

N  15.21  15.09  15.21 

The  ammonium  salt  of  uracil-5-ethylcarboxylate  is  charac- 
terized by  some  peculiar  properties.  When  a  not  too  dilute 
solution  of  the  ester  is  treated  with  a  little  strong  ammonia, 
long,  slender  needles  of  the  ammonium  salt  form  at  once. 
The  vapor  from  a  rod  dipped  in  ammonia  and  held  above 
the  surface  of  an  aqueous  solution  of  the  ester  will  cause  crys- 
tals to  form.  When  a  solution  of  the  salt  is  boiled,  ammonia 
escapes  and,  on  cooling,  nothing  separates  until  more  ammo- 
nia is  added.  If  the  solution  is  concentrated  by  heating, 
the  free  ester  separates.  The  ammonium  salt  is  insoluble, 
or  difficultly  soluble  in  alcohol.  An  aqueous  solution  of  the 
ester  was  precipitated  with  ammonia  and  the  precipitate  was 
dried  over  calcium  chloride.  The  needles  thus  obtained  melted 
at  about  220°  to  an  oil  that  effervesced.  Nitrogen  determina- 
tion (Kjeldahl) : 

Calculated  for 
C7H804N2  NH3.H20.  Found. 

N  19.13  19.33 

When  uracil-5-carboxylic  ethyl  ester  is  warmed  with  aqueous 
hydrochloric  acid  it  is  readily  saponified  and  uracil-5-carboxylic 
acid  is  obtained. 

HN CO 

I  I 

Uracil-5-carboxylic  Acid,    OC  CCO2H.H2O.  — This   acid 

HN CH 

can  be  prepared  directly  from  the  condensation  product  of 
ethoxymethylenemalonic  ester  and  ethylpseudothiourea  hy- 
drobromide,  or,  in  other  words,  from  the  potassium  salt  of 
2-ethylmercapto-5-carbethoxy-6-oxypyrimidine,  without  the 


400  Wheeler,  Johnson  and  Johns. 

isolation  of  the  above  intermediate  products,  by  simply  dissolv- 
ing the  salt  in  a  moderate  amount  of  strong  hydrochloric  acid 
and  evaporating  to  dryness  on  the  steam-bath.  If  the  prod- 
uct contains  sulphur,  the  operation  is  repeated.  The  resi- 
due is  then  crystallized  from  water  as  the  acid  is  practically 
insoluble  in  alcohol.  It  is  difficultly  soluble  in  water  and  sepa- 
rates in  the  form  of  colorless,  characteristic,  minute  pyramids 
with  rough  faces.  Or  small  prisms  form,  the  faces  sometimes 
alternating  with  those  of  a  pyramid.  The  crystals  contain 
iH2O,  which  is  given  off  on  heating  above  100°.  The  acid 
melts  partially,  but  quite  sharply,  at  278°,  with  energetic 
effervescence.  The  aqueous  solution  reddens  litmus  and  it 
gives  no  immediate  precipitate  with  lead  or  copper  acetate, 
or  barium  chloride.  Analysis : 

I.  0.5002  gram  substance,  dried  at  about  50°,  lost  0.0502 
gram  of  water  when  heated  for  i  hour  at  122° 

II.  0.5486  gram  substance  lost  0.0561    gram  water  when 
heated  for  2  hours  at  io5°-uo°. 

Calculated  for  Found. 

C6H404N2.H20.  I.  II.  III. 

H2O        IO.34        10.03      10.22      10.02 

N  16.09  16.15         16.03         16.26 

Nitrogen  determination  of  the  anhydrous  acid : 

Calculated  for  Found. 

C5H404N2.  I.  II.  III. 

N  17.94  17-88         17.99         17.91 

Nitrogen  was  determined  by  Kjeldahl's  method  except  in 
Analysis  III.  The  acid  used  for  Analysis  III.  (water)  and 
Analysis  VI.  was  obtained  by  the  saponification  of  uramido- 
methylenemalonic  ester.  The  other  samples  were  obtained 
from  the  potassium  salt  described  above. 

Behavior  on  Heating. — About  0.5  gram  of  the  acid  was 
heated  in  a  test  tube,  immersed  in  a  sulphuric  acid  bath,  at 
a  temperature  a  little  above  its  melting  point  until  efferves- 
cence ceased.  The  dark-colored  product  was  boiled  with 
water  and  animal  charcoal  and  the  solution  concentrated. 
On  cooling,  the  characteristic  crystals  of  uracil  separated, 
melting  or  effervescing  at  335°.  Analysis  (Kjeldahl) : 


Researches  on  Pyrimidines.  401 

Calculated  for 


Found. 

N  25.00  24.89 

Action  of  Acids:  Formation  of  Uracil. — The  action  of  20 
per  cent  sulphuric  acid  was  tried  as  follows:  Fifty-five-hun- 
dredths  gram  of  the  acid  potassium  salt  of  uracil-5-carboxylic 
acid  was  sealed  in  a  tube  with  5  cc.  of  sulphuric  acid,  sp.  gr.  = 
1.15,  and  heated  at  i6o°-i69°  for  2  hours.  On  opening  the 
tube,  carbon  dioxide  escaped  and  the  minute  microscopic 
needles  that  had  separated,  after  washing  with  water,  were 
found  to  melt  at  336°  without  further  purification.  A  nitrogen 
determination  agreed  with  the  calculated  for  uracil : 

Calculated  for 

C4H4O2N2.  Found. 

N  25.00  24.97 

The  needles  weighed  0.25  gram,  which  amount  is  71  per 
cent  of  the  calculated,  or,  allowing  for  solubility,  it  is  prac- 
tically a  theoretical  yield. 

The  Action  of  Concentrated  Hydrochloric  Acid. — One  gram 
of  uracil-5-carboxylic  acid  was  boiled  with  about  50  cc.  of 
concentrated  hydrochloric  acid,  using  a  return  condenser, 
for  1 8  hours.  The  acid  was  then  evaporated  and  the  residue 
was  crystallized  from  water,  whereupon  over  0.3  gram  of 
uracil  separated. 

Esterification:  Methyl  Uracil- 5-carboxylate, 
HN CO 

I 

CCO2CH3. — When  uracil-5-carboxylic  acid  is  warmed 

I  II 

HN CH 

with  acids  in  methyl  or  ethyl  alcohol,  it  is  smoothly  esterified. 
One  gram  of  the  anhydrous  acid  was  suspended  in  75  cc.  of 
methyl  alcohol,  to  which  5  drops  of  concentrated  sulphuric 
acid  had  been  added.  On  boiling  for  8  hours,  all  of  the  acid 
went  into  solution  and  on  evaporation  to  a  small  volume  a 
gelatinous  mass  was  formed.  This  gave  a  white  powder  when 
stirred  with  cold  water.  The  material  thus  obtained  was 
readily  soluble  in  hot  water  and  on  cooling,  short,  stout,  color- 


402  Wheeler,  Johnson  and  Johns. 

less  prisms  separated.     These  sintered  at  about  2 2  5°  and  decom- 
posed at  233°.     Nitrogen  determination  (Kjeldahl): 

Calculated  for  Pound. 

C6H604N2.  I.  II. 

N  16.47  16.62  16.58 

When  uracil-5-carboxylic  acid  was  warmed  with  ethyl 
alcohol  and  sulphuric  acid,  the  ethyl  ester  described  above 
was  obtained.  It  was  identified  by  the  melting  point  236° 
and  by  its  behavior  towards  ammonia. 

The  Acid  Potassium  Salt,  C5H3O4N2K.C5H4O4N2.— When  uracil- 
5-carboxylic  acid  and  either  sodium  or  potassium  hydroxide 
were  mixed,  in  molecular  proportions,  the  hot  aqueous  solu- 
tion, on  cooling,  deposited  an  acid  salt.  For  example,  8 
grams  of  the  hydrous  acid  and  2.5  grams  of  potassium  hy- 
droxide were  dissolved  in  about  500  cc.  of  boiling  water. 
On  cooling,  2  grams  of  slender,  needle-like  crystals  separated. 
These  effervesced  at  about  270°.  Analysis: 

Calculated  for  Found. 

C10H708N4K.  I.  II.  III. 

N  16.00  15.89        15.98         

K  11.14  10.87 

The  Monopotassium  Salt,  u.  C5H3O4N2K. — Three  grams  of 
uracil-5-carboxylic  acid  were  dissolved  in  a  solution  of  2 
grams  of  potassium  hydroxide,  1.9  grams  =  2  mols.,  in  about 
20  cc.  of  water ;  on  concentrating  on  the  steam-bath  small  needles 
separated.  These  were  dried  at  about  55°.  Nitrogen  deter- 
minations (Kjeldahl) : 

Calculated  for  Found. 

C6H2O4N2.K2.         C6H3O4NaK.  I.  II. 

N  12.06  14.43  14.72         14.71 

The  analyzed  material  showed  no  signs  of  melting  at  295°. 
On  dissolving  the  dried  salt  in  water  the  solution  was  found 
to  be  neutral  to  litmus  and  turmeric.  It  gave  a  white,  insolu- 
ble precipitate  with  lead  acetate  and  the  hot  solution  gave 
a  crystalline  precipitate  with  barium  chloride. 

The  Barium  Salt,  (C5H3O4N2)2Ba.— Barium  chloride  was 
added,  in  excess,  to  a  hot,  dilute,  neutral  solution  of  the  above 


Researches  on  Pyrimidines.  403 

potassium  salt.  Stout,  microscopic  prisms,  pointed  at  both 
ends,  crystallized  out.  These  were  almost  insoluble  in  hot 
water.  They  were  dried  at  no°-i2o°  but  did  not  give  off 
water. 

Calculated  for 

Ci0H6O8N4Ba.  Found. 

Ba  30.64  28.83 

The  Sillier  Salt.  —  Two  grams  of  the  monopotassium  salt  were 
dissolved  in  100  cc.  of  water  and  1.7  grams  of  silver  nitrate 
in  50  cc.  of  water  were  slowly  added,  with  stirring,  in  order 
to  prevent  a  local  excess  of  the  nitrate.  A  white,  bulky,  gelatin- 
ous precipitate  separated  which  did  not  alter  or  become  granu- 
lar on  warming.  The  solution  was  diluted  with  100  cc.  of  water 
and  allowed  to  settle;  the  precipitate  was  washed  by  decan- 
tation  and  then  filtered  on  cheese  cloth.  It  was  dried  at  100° 
for  analysis. 

One  molecular  proportion  more  of  silver  nitrate  was  then 
added  to  the  filtrate.  This  gave  a  slight  precipitate.  On 
adding  0.5  gram  of  potassium  hydroxide,  in  a  little  water, 
a  quantity  of  white  salt  was  again  precipitated,  apparently 
equal  in  amount  to  that  which  was  obtained  at  first.  The 
analytical  results  did  not  agree  with  those  calculated  for  a 
pure  salt.  They  indicate  that  the  precipitate  was  a  mixture 
of  a  mono-  and  a  disilver  salt.  A  sample  prepared  by  taking 
molecular  proportions  of  acid,  sodium  hydroxide  and  silver 
nitrate  gave  no  better  results  (Analyses  III.  and  IV.). 

Calculated  for     Calculated  for  Found. 

C5H3O4N2Ag.       CsHgO^NaAga.      I.  II.  III.  IV. 


N  10.64  7.56     8.86     8.54     ........ 

Ag          41.64  58.37     ........     49.0     51.5 

The  following  shows  that  uracil-5-carboxylic  acid  gives  a 
disilver  salt:  Eleven  grams  of  the  acid,  dissolved  in  water 
and  treated  with  2  molecules  of  sodium  hydroxide  and  2  mole- 
cules of  silver  nitrate,  gave  a  pure  white  precipitate  which, 
when  dry,  weighed  2  1  grams.  The  calculated  for  a  mono  salt 
is  1  6  grams,  that  for  a  disilver  salt  is  23.4  grams. 

Dimethyl  Derivative.  —  Ten  grams  of  the  disilver  salt  were 
suspended  in  ether  and  15  grams  of  methyl  iodide  were  added. 


404  Wheeler,  Johnson  and  Johns. 

The  mixture  was  heated  in  a  closed  tube  at  98°-  103°  for  1.5 
hours.  The  ether  and  excess  of  methyl  iodide  were  evaporated 
and  the  residue  extracted  with  alcohol.  This  gave  a  gummy 
extract  which,  when  recrystallized  from  alcohol,  yielded  small 
prisms,  melting  at  25^-2  56°  ,  with  slight  effervescence.  The 
substance  dissolved  with  difficulty  in  hot  alcohol  and  was 
moderately  soluble  in  hot  water.  It  had  a  very  bitter  taste. 
A  nitrogen  determination  (Kjeldahl),  made  after  drying  at 
uo°-i2o°,  gave: 

Calculated  for 
C7H8O4N2.  Found. 

N  15.21  15.16 

A  diethyl  derivative  was  prepared  in  a  similar  manner.  It 
crystallized  from  alcohol,  in  which  it  is  moderately  soluble 
when  cold,  in  the  form  of  clusters  of  blunt  prisms,  melting  at 
i62°-i63°.  In  both  of  these  reactions  of  the  silver  salt  the 
chief  product  isolated  was  the  free,  unaltered  acid  which 
was  obtained  by  extracting  the  residue  with  water.  A  nitro- 
gen determination  (Kjeldahl),  in  the  case  of  the  material 
melting  at  162°-!  63°,  showed  that  it  was  a  diethyl  deriva- 
tive: 

Calculated  for 

Found. 


N  13.20  13.45 

Ethoxymethylenemalonic  ester  and  methyl  pseudothio- 
urea  hydriodide  were  condensed,  using  i  molecular  propor- 
tion of  potassium  hydroxide.  Under  these  conditions  |  the 
free  2-methylmercapto-5-carbethoxy-6-oxypyrimidine  did  .not 
separate  but,  instead,  a  poor  yield  of  a  basic  hydriodide  of 
the  ester  was  obtained.  A  nitrogen  determination  (Kjel- 
dahl) agreed  with  the  calculated  for  a  2:  i  salt: 

Calculated  for 
,:.;.,          (C8HioO8N2S)2HL  Found. 

N  10.  o  10.1 

This  salt  forms  needles  from  alcohol;  when  boiled  with  water, 
mercaptan  was  given  off.  It  had  no  definite  melting  point. 


Researches  on  Pyrimidines.  405 

2-Methylmercapto-5-carboxyl-  6  -oxypyrimidine, 
HN CO 

I  I 

CH3SC  CCO2H.— This    was    obtained    by   warming    the 

I!         II 
N CH 

above  salt  with  potassium  hydroxide  and  then  precipitating 
with  hydrochloric  acid.  It  crystallized  from  hot  water  in 
well  developed,  colorless  prisms,  melting,  to  a  clear  oil,  at  235°. 
Nitrogen  determination  (Kjeldahl) : 

Calculated  for 
C6H6O3N2S.  Found. 

N  15.05  14.71 

Our  chief  experiments  were  performed  with  the  ethyl- 
mercapto  derivatives,  since  they  are  more  insoluble  than  the 
methyl  compounds. 

NEW  HAVEN,  CONN., 
January,  1907. 


[Reprinted  from  the  American  Chemical  Journal,    Vol.  XXXVII,    No.  6. 
June,  1907.] 


Contributions  from  the  Sheffield  Laboratory  of  Yale  University. 

CXUV.— RESEARCHES  ON  PYRIMIDINES:  SOME  CON- 
DENSATION PRODUCTS   OF  A  SUBSTITUTED 
PSEUDOTHIOUREA:     SYNTHESIS    OF 
i-METHYLURACIL. 

BY  TREAT  B.  JOHNSON  AND  F.  W.  HEYL. 

(TWENTIETH  PAPER.) 

Substituted  ureas  apparently  do  not  condense  with  /2-ketone 
esters  to  form  pyrimidines.  While  urea  reacted  with  ethyl 
acetoacetate  to  form  4-methyluracil,  II.,  Behrend1  obtained 
no  condensation  products  corresponding  to  methyluracil 
when  phenylurea,  diphenylurea  and  dimethylurea  were 
treated  with  this  ketone  ester. 

The  alkyl  derivatives  of  4-methyluracil,  II.,  in  which  the 
alkyl  groups  are  linked  to  nitrogen,  have  all  been  prepared 
by  heating  this  pyrimidine  with  alkyl  halides2  in  presence 
of  alkalis,  or  by  condensing  ^-alkyluraminocrotonic  esters, 
III.,  to  pyrimidines,  by  treatment  with  alkali.3  The  corre- 
sponding alkyl  derivatives  of  uracil,  I.,  have  not  been  de- 
scribed. 

1  Ann.  Chem.  (Liebig),  229,  15;  233,  i. 

1  Behrend:  Ann.  Chem.  (I^iebig),  229,  23;  231,  256  ;  253,  67.  Hagen  :  Ibid., 
244,  2.  Hoffman:  Ibid.,  253,  73.  Behrend  and  Dietrich  :  Ibid.,  309,  260.  Behrend 
and  Meyer  :  Ber.  d.  chem.  Ges.,  33,  624. 

3  Behrend  and  Meyer  :  Ber.  d.  chem.  Ges.,  33,  621.  Behrend  and  Buchholz  :  Ann. 
Chem.  (I^iebig),  314,  209.  Behrend  and  Thurm :  Ibid.,  323,  160.  Behrend  and  Hesse: 
Ibid.,  329,  341. 


Researches  on  Pyrimidines.  629 

NH CO  NH CO  RNH       COOC2H6 

III  II 

CO       CH  CO        CH      ,  CO       CH 

I           II                   I             II                          I  II 

NH  — CH  NH CCH3  NH C.CH3 

I.  II.  III. 

It  has  been  shown  in  papers  from  this  laboratory1  that 
elementary  pseudothioureas  condense  more  readily  with 
aldehyde  and  ketone  esters  than  the  normal  oxygen  ureas. 
In  this  paper  we  describe  the  behavior  of  an  aliphatic,  mono- 
substituted  pseudothiourea  towards  some  ketone  esters. 
We  find  that  they  condense  to  give  substituted  mercapto- 
pyrimidines,  which  are  easily  converted  to  uracil  derivatives 
by  digesting  with  hydrochloric  acid. 

Theoretically,  2  isomeric  mercaptopyrimidines — i-methyl- 
2-ethylmercapto-6-oxypyrimidine,  V.,  or  3-methyl-2-ethyl- 
mercapto-6-oxypyrimidine,  VI.,  might  be  formed  by  con- 
densing ethyl  formylacetate  with  methyl  pseudoethylthio- 
urea,  IV.  We  find  that  they  condense  to  give  i-methyl-2- 

CHSN CO  N CO 

II  II         I 

HN:C(SC2H5)NHCH3  ,      C2H5SC       CH    ,   C2H5SC       CH 

IV.  II          ||  ||          II        . 

N CH         CH3N CH 

V.  VI. 

ethylmercapto-6-oxypyrimidine,    V.     We    obtained    no    evi- 
dence of  the  formation  of  the  isomeric  derivative,  VI.: 

CH3NH  COOC2H5 

C,H5SC         +         CH  = 

II  II 

NH          HOCH 

CH3N — CO 

C2H5SC      CH  +  C2H5OH  +  H,O. 

II        II 
N  — CH 
v. 

1  Wheeler  and  Merriam  :  THIS  JOURNAL,  29,  478  (1903).  Wheeler  and  Johnson  : 
Ibid.,  31,  591  (1904).  Wheeler  and  Bristol :  Ibid.,  33,  437  (1905). 


630  Johnson  and  Heyl. 

The  same  mercaptopyrimidine,  V.,  was  also  obtained  when 
2-ethylmercapto-6-oxypyrimidine1  was  warmed  in  alcohol 
with  molecular  proportions  of  potassium  hydroxide  and  methyl 
iodide. 

NH CO 

C2HBSC          CH  +  KOH  +  CH3I     = 

II  II 

N CH 

CH3N CO 

C2H5SC      CH  +  KI  +  H2O. 

II        II 

N CH 

v. 

When  the  mercaptopyrimidine,  V.,  was  digested  with  con- 
centrated hydrochloric  acid,  it  was  converted  quantita- 
tively into  i-methyluracil,  VII.,  with  evolution  of  ethyl^mer- 
captan. 

CH3N CO  CHSN CO 

II  II 

C2H5SC       CH  +  H20          ==       C,H6SH     +     CO        CH 

II        II  I  II 

N CH  NH CH. 

VII. 

The  structure  of  the  methyluracil,  VII.,  and  the  corre- 
sponding mercapto  derivative,  V.,  was  shown  in  the  fol- 
lowing manner:  It  was  converted  smoothly  into  i-methyl- 
2,6-dioxy-5-nitropyrimidine,2  VIII.,  by  treatment  with  fum- 
ing nitric  and  sulphuric  acids.  Our  nitromethyluracil,  VIII., 

CHSN CO  CH3N CO 

CO       CH  +  HNO3  =  CO        CNO2  +  H2O, 

'I            II                                                 I  II 

NH CH  NH CH 

VIII. 
was    anhydrous    and    melted    at    264°-265°.     The    isomeric 

1  Wheeler  and  Merriam  :  Loc.  cit. 

2  Behrend  and  Thurm :  Loc.  cit. 


Researches  on  Pyrimidines.  631 


3-methyl-2,6-dioxy-5-nitropyrimidine1    contains     i     molecule 
of  water  of  crystallization  and  melts  at  255°-256°. 

Methyl  pseudoethylthiourea  condensed  with  ethyl  aceto- 
acetate  to  give  i,4-dimethyl-2-ethylmercapto-6-oxypyrimi- 
dine,  IX.  Its  structure  was  confirmed  by  the  fact  that  it 
was  converted  into  Behrend's  /3-dimethyluracil  or  i,4-di- 
methyl-2,6-dioxypyrimidine,2  X.,  by  treatment  with  hydro- 
chloric acid. 

CH3NH  COOC2H5 

C2H5SC       +       CH 

II  II 

NH      HOCCH3 

CH3N CO 

I  I 
C2H5SC       CH 

II  II 

N CCH3  NH CCH3. 

IX.  X. 

It  is  interesting  to  note  that  methylurea  and  methylthio- 
urea  condense  with  ethyl  cyanacetate  to  give  2,6-dioxy-3- 
methyl-4-aminopyrimidine,3  XI.,  and  2-thio-3-methyl-4-amino- 
6-oxypyrimidine,4  XII.,  respectively, 

NH CO  NH CO 

I  I  I 

CH  ,  CS         CH 

I  II 

CH3N CNH2 

XI. 

It  was  shown  in  a  previous  paper5  that  pseudoethylthio- 
urea condenses  with  diethyl  formylgly collate  to  form  2-ethyl- 
rnercapto-5-ethoxy-6-oxypyrimidine,  XIII.  We  find  that 
ethyl  formylphenoxy  acetate6  also  condenses  with  this 
pseudothiourea  to  give  2-ethylmercapto-5-phenoxy-6-oxy- 
pyrimidme,  XIV. : 

1  Behrend  and  Thurm  :  Loc.  cit. 

2  Behrend  and  Dietrich  :  Loc.  cit.    Behrend  and  Thurm  :  Loc.  cit. 
8  Conrad  :  Ann.  Chem.  (Liebig),  340,  314. 

4  Trauber  and  Winter:  Archiv.'Pharm.,  244,  n  (1906). 

5  Johnson  and  McCollum  :  J.  Biolog.  Chem.,  i,  437. 

6  Johnson  and  McCollum  :  Loc.  cit. 


632  Johnson  and  Heyl. 

NH — CO  NH CO 

II  II 

C2H6SC          COC2H5     ,  C2H6SC  COC6H5 

II  II  II  II 

N -CH  N CH. 

XIII.  XIV. 

EXPERIMENTAL   PART. 

Methylpseudoethylthiourea  Hydriodide, 

CHgNHCCSCjHg) :  NH.HI,  was  prepared  by  treating  mono- 
methylthiourea  with  ethyl  iodide.  It  was  obtained  as  a  heavy 
oil,  which  finally  solidified  in  a  vacuum  over  sulphuric  acid. 
The  salt  was  extremely  hydroscopic  and  on  prolonged  ex- 
posure to  the  atmosphere  changed  to  an  oil. 

i  -Methyl-2-ethylmercapto-6-oxypyrimidine, 
CH3N CO 

C2H5SC       CH. — Molecular  proportions  of  the  above  pseudo- 

II         II 
N CH 

urea  hydriodide  and  the  sodium  salt  of  ethyl  formylacetate 
were  separately  dissolved  in  the  least  possible  quantities  of 
cold  water.  The  2  solutions  were  then  combined  and  treated 
with  an  aqueous  solution  containing  i  molecular  proportion 
of  potassium  hydroxide.  The  mixture  was  allowed  to  stand 
at  ordinary  temperatures  for  about  12  hours  and  then  heated 
for  a  few  hours  on  the  steam  bath.  No  crystalline  material 
deposited  on  cooling.  The  mercaptopyrimidine  was  ex- 
tracted with  ether  and  the  ether  allowed  to  evaporate  spon- 
taneously, when  the  pyrimidine  deposited  in  prismatic  crys- 
tals. They  were  extremely  soluble  in  hot  alcohol  and  in  ether, 
but  soluble  with  difficulty  in  cold  water.  The  pyrimidine  de- 
posited from  alcohol  in  stout  prisms,  that  melted  at  79°- 
80°,  without  effervescence,  to  a  clear  oil.  It  was  soluble  in 
dilute  hydrochloric  acid  and  was  precipitated  from  the  acid 
solution  by  phosphotungstic  acid.  Analysis  (Kjeldahl) : 

Calculated  for 
C7H10ON2S.  Found. 

N  [16.47  16.6 


Researches  on  Pyrimidines.  633 

The  same  mercaptomethylpyrimidine  was  also  obtained 
when  2-ethylmercapto-6-oxypyrimidine1  was  treated  with 
methyl  iodide  under  the  following  conditions :  One  molecu- 
lar proportion  of  potassium  hydroxide  and  9.8  grams  of 
2-ethylmercapto-6-oxypyrimidine  were  dissolved  in  50  cc. 
of  95  per  cent  alcohol.  Twelve  grams  of  methyl  iodide 
were  then  added  and  the  solution  digested  on  the  steam  bath 
until  it  gave  no  alkaline  reaction  with  turmeric.  It  was  then 
cooled,  ^the  insoluble  potassium  iodide  separated  by  filtration 
and  the  excess  of  alcohol  removed  by  evaporation  on  the 
steam  bath.  We  obtained  a  syrup  that  would  not  solidify 
on  cooling.  After  treatment  with  a  small  volume  of  water, 
to  remove  any  potassium  iodide,  the  mercaptopyrimidine 
deposited  in  well-developed  prisms.  They  were  crystallized 
from  alcohol  and  melted  at  79°-8o°,  to  a  clear  oil.  When 
mixed  with  the  above  mercaptopyrimidine  the  melting  point 
was  not  changed.  Analysis  (Kjeldahl): 

Found. 
Calculated  for  .  •> 


I.  II. 

N  16.47  16.33  16.6 

2-Ethylmercapto-6-oxypyrimidine  was  recovered  unaltered 
after  heating  with  i  molecular  proportion  of  methyl  iodide 
for  2  hours,  at  i55°-i65°. 

i -Methyl-2,6-dioxypyrimidine    (i -Methyluracil) , 
CH3N CO 

CO        CH. — One   and   five-tenths    grams    of    i -methyl- 

I  II 

NH CH 

2-ethylmercapto-6-oxypyrimidine  were  digested  with  15  cc. 
of  20  per  cent  hydrochloric  acid  until  the  evolution  of  ethyl 
mercaptan  ceased.  When  the  acid  solution  was  evaporated 
to  dryness  the  methyluracil  deposited  in  microscopic,  pris- 
matic crystals  that  melted  sharply  at  i74°-i75°,  without 
effervescence,  to  a  clear  oil.  It  was  extremely  soluble  in 
cold  water  and  alcohol  but  insoluble  in  benzene.  It  was  not 

1  Wheeler  and  Merriam. 


634  Johnson  and  Heyl. 

precipitated  from  its  aqueous  solution  with  picric  acid.  It 
was  dried  for  analysis  at  110°  (Kjeldahl): 

Calculated  for 
C5H6O2N2.  Found. 

N  22.22  22.21 

When  uracil  was  heated  with  2  molecular  proportions  of 
methyl  iodide  at  i86°-2oo°,  for  2  hours,  it  was  recovered 
unaltered. 

Calculated  for 
C4H402N2. 

N  25.  o 

CH8N 

i-Methyl-^-nitro-6-oxypyrimidine,1  CO        CNO2.  —  Four 

NH CH 

and  three-tenths  grams  of  i -methyluracil  were  dissolved  in 
a  mixture  of  1 5  cc.  of  fuming  nitric  acid  and  1 5  cc.  of  concen- 
trated sulphuric  acid,  and  the  solution  heated  on  the  steam 
bath  until  effervescence  practically  ceased.  The  acid  solu- 
tion was  then  poured  upon  crushed  ice,  when  a  heavy,  granular 
precipitate  deposited.  The  compound  was  soluble  with  difficulty 
in  cold  water,  but  deposited  from  hot  water  in  stout,  prismatic 
crystals  that  melted  at  264°-265°,  with  effervescence,  to  a 
clear  oil.  It  deposited  from  hot  alcohol  in  hexagonal  plates. 
When  the  compound  was  mixed  with  some  nitrouracil  the 
melting  point  was  lowered  to  240°.  It  did  not  contain 
water  of  crystallization.  Analysis  (Kjeldahl): 

Calculated  for 
C5H504N3.  Found. 

N  24.56  24.8 

CH3N CO 

i-Methyl-2,6-dioxy-5-brompyrimidine,          CO      CBr.  —  One 

I          II 
NH— CH 

gram  of  methyluracil  was  dissolved  in  8  cc.  of  glacial  acetic 
acid  and  1.3  grams  of  bromine  added.  Hydrobromic  acid 
was  evolved  at  once  and  the  bromine  derivative  deposited 

1  Behrend  and  Thurm  :  Loc.  cit. 


Researches  on  Pyrimidines.  635 

in  prismatic  crystals.  The  compound  was  soluble  in  hot 
water  but  insoluble  in  cold.  It  deposited  from  95  per  cent 
alcohol  in  well-developed,  transparent  prisms  that  melted  to 
a  clear  oil,  at  228°-229°.  Analysis  (Kjeldahl): 

Calculated  for 
C6H6OjNaBr. 

N  13-65 


i~Ethyl-2t6-dioxypyrimidine  (i-Ethyluracif) ,          CO        CH. 

NH CH 

— This  compound  was  prepared  from  2-ethylmercapto-6- 
oxypyrimidine  as  follows:  The  mercaptopyrimidine  was 
first  converted  into  i-ethyl-2-ethylmercapto-6-oxypyrimidine 
by  treatment  with  potassium  hydroxide  and  ethyl  iodide, 
as  in  the  preparation  of  i-methyl-2-ethylmercapto-6-oxy- 
pyrimidine.  The,;,  diethylmercaptopyrimidine  was  obtained 
as  an  oil,  which,  without  purification,  was  digested  with  con- 
centrated hydrochloric  acid  until  the  evolution  of  ethyl 
mercaptan  ceased.  When  the  hydrochloric  acid  was  removed 
by  evaporation  the  ethyluracil  was  obtained  as  a  crystalline 
deposit.  The  yield  was  practically  quantitative.  It  was 
very  soluble  in  hot  water  and  alcohol.  It  deposited  from 
benzene  in  foliated  prisms  that  melted  at  I73°-I74°  to  a 
clear  oil.  Analysis  (Kjeldahl): 

Calculated  for 

C6H802N2.  Found. 

N  20.00  19.75 

CH3N CO 

i,4-Dimethyl-2,6-dioxypyrimidine,  CO        CH.  —  This 

I  II 

NH CCH3 

compound  has  been  prepared  by  Behrend  and  his  co-workers.1 
We  obtained  it  by  condensing  methylpseudoethylthiourea 
with  ethyl  acetoacetate  to  ^form  i,4-dimethyl-2-ethylmercapto- 
pyrimidine.  When  this  mercaptopyrimidine  was  boiled  with 
concentrated  hydrochloric  acid  the  dime  thy  luracil  was  formed 

»  Loc.  cit. 


636  Johnson  and  Heyl. 

with  evolution  of  ethyl  mercaptan.  It  deposited  from  hot 
water  in  prismatic  crystals,  that  melted  at  260°  to  an  oil. 
The  compound  agreed  in  its  properties  with  Behrend's  1,4- 
dimethyluracil.  Analysis  (Kjeldahl): 

Calculated  for 

C6H8O2N2.  Found. 

N  2O  .  OO  2O  .  OO 

Sodium  Salt  of  Ethyl  <x-Phenoxy-fi-oxyacrylate, 
NaOCH:C(OC6H5)COOC2H5.—  Three  and  two-tenths  grams 
of  sodium  wire  and  i  molecular  proportion  of  absolute  alco- 
hol, 6.3  grams,  were  digested  in  anhydrous  ether  until  the 
formation  of  sodium  ethylate  was  complete.  Twenty-five 
grams  of  ethyl  phenoxyacetate  and  10.3  grams  of  ethyl 
formate  were  then  added  and  the  ether  solution  allowed  to 
stand  over  night,  when  a  colorless,  crystalline  sodium  salt 
deposited.  It  was  dried  in  a  desiccator  over  sulphuric  acid. 
Analysis  : 

Calculated  for 

Found. 


Na  10.00  9.65 

The  free  ethyl  ester  was  obtained  as  a  heavy  oil  when  an 
aqueous  solution  of  the  sodium  salt  was  treated  with  sulphuric 
acid.  It  underwent  decomposition  when  we  attempted 
to  distil  it  under  diminished  pressure. 

^jJHydrazone  of  Ethyl  Formylphenoxy  acetate, 
QaHgNHNtCHCHCOCeHJCOOCaHs.—  Five  grams  of  ethyl 
formylphenoxyacetate  and  3  grams  of  phenylhydrazine  were 
warmed  together  in  a  water-bath,  for  30  minutes.  They  re- 
acted with  evolution  of  heat  to  form  a  yellow,  crystalline 
compound.  It  deposited  from  warm,  95  per  cent  alcohol 
in  yellow  prisms,  that  melted  at  2i9°-22i°,  with  violent  effer- 
vescence. Analysis  (Kjeldahl)  : 

Calculated  for 
CnHi8O3N2.  Found. 

N  9-39  9-3 


Preparation  of  Potassium  Ferricyanide.  637 

2-Ethylmercapto-5-phenoxy-6-oxypyrimidine} 
NH CO 

C2H5SC  COC6H5. — This  pyrimidine  was  formed  by  con- 

'    II  II 

N CH 

densing  pseudoethylthiourea,  in  aqueous  solution,  with  the 
sodium  salt  of  ethyl  a-phenoxy-/?-oxyacrylate.  After  stand- 
ing for  6  hours  and  acidifying  with  acetic  acid,  the  pyrimidine 
deposited  in  prismatic  crystals.  It  crystallized  from  alcohol 
in  transparent  prisms,  that  melted  at  159°  to  an  oil.  It 
responded  to  a  test  for  sulphur.  Analysis  (Kjeldahl): 

Calculated  for 
Ci2Hi2O2N2S.  Found. 

N  11.29  ii  06 

NEW  HAVEN,  CONN., 
Feb.  15,  1907. 


IV.    RESEARCHES  ON  PYRIMIDINS:  ON  A  COLOR  TEST 
FOR  URACIL  AND  CYTOSIN. 

PLATE  II. 

(Twenty-first  Paper.) 
BY  HENRY  L.   WHEELER  AND  TREAT  B.  JOHNSON. 

(From  the  Sheffield  Laboratory  of  Yale  University.) 
(Received  for  publication,  April  19,  1907.) 

When  uracil  or  cytosin  is  dissolved  in  bromine  water  and  the 
solution  is  treated  with  an  aqueous  solution  of  barium  hydroxide 
in  excess,  a  purple  or  violet-blue  precipitate  or  color  is  produced 
even  in  dilute  solutions. 

The  formation  of  the  purple  precipitate  involves  several  inter- 
mediate reactions  that  are  explained  in  the  following  manner: 
Uracil  (I)  and  bromine  water  first  react  to  form  dibromoxyhy- 
drouracil  (II),  and  the  same  compound  is  also  obtained  wrhen 
cytosin  (III)  is  treated  with  bromine  water.  Dibromoxyhy- 
drouracil  is  very  sensitive  toward  alkalies.  When  treated  at 
ordinary  temperature  with  an  excess  of  barium  hydroxide  the  two 
atoms  of  bromine  are  replaced  by  hydroxyl  groups  and  isodialu- 
ric  acid  (IV)  is  formed.  Isodialuric  acid  then  undergoes  a  rear- 
rangement into  dialuric  acid  (V).1  Both  isodialuric  and  dialuric 
acids  give  a  violet-blue  precipitate  with  barium  hydroxide  as 
observed  by  Behrend  and  Roosen.2 


1  Behrend  and  Koch:  Ann.  d.  Chem.  (Liebig),  cccxv,  p.  246,  1901. 

2  Ann.  d.  Chem.,  (Liebig),  ccli,  p.  244,  1889. 

183 


184  Color  Test  for  Uracil  and  Cytosin 

N=C-NH3 

I      I 

OC      CH 

I        II 
HN— CH 

>*  III 


HN— CO 

I        I 
OC      CBr, 

I    I 

HN — CHOH 
II 


HN—  CO 

I         I    /OH 
OC       C< 

I      !XOH 

HN—  CHOH 
IV 


HN— CO 

I        I 
OC      CHOH 

I        I 
HN— CO 


HN—  CO 


OC     CH 

I        II 
HN— CH 

I 

That  the  present  test  involves  the  formation  of  dialuric  acid 
was  shown  as  follows:  The  freshly  prepared  barium  precipitate 
was  dissolved  in  hydrochloric  acid  and  the  barium  was  removed 
by  means  of  dilute  sulphuric  acid.  On  evaporating  this  solution 
then  in  a  desiccator  we  obtained  crystals  of  alloxantin  (VI). 
Dialuric  acid  undergoes  oxidation  in  the  air  to  alloxantin,1  while 
such  behavior  was  never  observed  in  the  case  of  isodialuricacid.2 


HN— CO 


OC      CHOH 


HN— CO 


HN— CO 


CO— NH 


OC      CH— O— COH  CO 

II  II 

HN— CO  CO— NH 

VI 


Behrend  was  the  first  to  show  that  certain  pyrimidins  give 
bromoxyhydro-derivatives.  For  example,  he  prepared  dibrom- 
oxyhydromethyluracil  (VII)3  from  4-methyluracil. 

1  Baeyer:  Ann.  d.  Chem.  (Liebig),  cxxvii,  p.  12,  1863. 

2  Behrend  and  Roosen:  Loc.  cit. 

*  Ann.  d.  Chem.  (Liebig),  ccxxix,  p.  18,  1885. 


Henry  L.  Wheeler  and  Treat  B.  Johnson       185 

This  compound  gives  no  color  with  barium  hydroxide.  Of 
more  interest  in  connection  with  the  test,  however,  is  the  fact 
that  the  similar  compound  from  thymin,  bromoxyhydrothymin 
(VIII) ,  described  by  Walter  Jones,1  also  gives  no  color  with  barium 
hydroxide.  Obviously  these  compounds  would  not  be  expected 
to  yield  dialuric  acid  on  treating  with  baryta  water. 

HN— CO  HN— CO 

II  II 

OC      CBr  OC      C  (CH3)  Br 

II  II 

HN— C  (CH3)  OH  HN— CHOH 

VII  VIII 

In  Richard  Burians'  interesting  work2  on  the  question  whether 
cytosin  is  a  primary  product  or  whether  it  results  by  secondary 
decomposition  of  some  other  substance  when  the  nucleic  acids 
are  submitted  to  hydrolysis,  he  boiled  guanin  and  adenin  mixed 
with  various  carbohydrates  in  30-40  per  cent  sulphuric  acid.  He 
did  not  obtain  cytosin  by  this  treatment,  but  instead,  from 
guanin  2-amino-6-oxypyrimidin  (isocytosin)  was  formed  (IX).3 
The  synthesis  of  this  pyrimidin  has  been  described  by  us.4  On 
the  other  hand,  adenin  (5  grams)  gave  6-aminopyrimidin  (X),5 
(0.5  gram).  These  pyrimidins  are  therefore  to  be  considered  in 
the  test. 

HN— CO  N=C-NH2 

I  I       I 

H2N-C     CH  HC     CH 

II        II  II      II 

N— CH  N— CH 

IX  X 

When  isocytosin  is  treated  with  bromine  water  it  yields  a 
bromine  derivative  that  is  not  identical  with  dibromoxyhydro- 
uracil.  This  substance  gives  an  intense  blue  color  on  carefully  add- 
ing a  solution  of  barium  hydroxide.  It  is  a  more  decided  blue 

1  Zeitschr.  f.  physiol.  Chem.,  xxix,  p.  20,  1900. 

2  Ergeb.  d.  Physiol.  (Asher-Spiro),  v,  p.  794,  1905. 

3  Amer.  Chem.  Journ.,  xxix,  p.  492,  1903. 

4  Buttner:  Ber.  d.  deutsch.  chem.  Gesellsch.,  xxxvi,  p.  2232,  1903. 
8  Wheeler  and  Bristol:  Amer.  Chem.  Journ.,  xxxiii,  p.  458,  1905. 


i86  Color  Test  for  Uracil  and  Cytosin 

than  that  which  results  from  dibromoxyhydrouracil  and,  what 
is  more  important,  it  is  readily  distinguished  from  the  latter  by 
immediately  disappearing  on  adding  an  excess  of  the  barium 
hydroxide  solution.  This  behavior  serves  as  a  delicate  test  for 
isocytosin. 

Finally  6-aminopyrimidin  was  prepared  by  a  new  method; 
starting  with  2-thiouracil,1  which  can  readily  be  obtained  in 
quantity,  2,6-dichlorpyrimidin  was  prepared  by  means  of  phos- 
phorous pentachloride.2  The  dichlorpyrimidin  then  gave  2-chlor- 
6-aminopyrimidin  with  alcoholic  ammonia,  and  this  was  found  to 
reduce  smoothly  to  6-aminopyrimidin  when  warmed  with  con- 
centrated hydriodic  acid. 

The  material  thus  obtained  gave  no  color  whatever  with  bro- 
mine water  and  barium  hydroxide. 


THE    TEST. 

Bromine  water  is  added  to  about  5  cc.  of  the  solution  to  be 
examined  until  the  color  is  permanent.  Too  much  bromine  is 
to  be  avoided  since  a  large  excess  interferes  with  the  test. 

It  is  advisable,  especially  when  only  small  quantities  of  cytosin 
or  uracil  are  present  to  remove  the  excess  of  bromine  by  passing 
a  stream  of  air  through  the  solution.  Then  on  adding  barium 
hydroxide  in  excess  the  purple  color  is  almost  immediately  pro- 
duced. 

Very  dilute  solutions  do  not  give  the  test.  In  such  cases  on 
evaporating  to  dryness  and  then  taking  up  the  material  in  a  little 
bromine  water,  removing  the  excess  of  bromine,  etc.,  a  quantity 
as  small  as  o.ooi  gram  of  uracil  gives  a  decided  bluish-pink  or 
lavender  color. 

In  applying  the  test  in  the  case  of  cytosin  it  is  advisable  to 
warm  or  boil  the  solution  with  bromine  water,  cool,  and  then 
apply  the  test  as  above,  being  sure  to  have  a  slight  excess  of  bro- 
mine present  before  adding  barium  hydroxide.  Dibromoxyhy- 
drouracil is  decomposed  by  prolonged  boiling  with  water  into 

1  Gabriel:  Ber.  d.  deutsch.chem.  Gesellsch.,x'x.'x.vin,  p.  1690, 1905;  Johnson 
and  Menge:  This  Journal,  ii,  p.  115,  1906. 

2  Gabriel:  Ber.  d.  deutsch.  chem.  Gesellsch.,  xxxviii,  p.  1690,  1905. 


THE  JOURNAL  OF   BIOLOGICAL   CHEMISTRY.       VOL.    III.       PLATE    II. 


Henry  L.  Wheeler  and  Treat  B.  Johnson       187 

5-bromuracil,1  which  gives  no  color  with  barium  hydroxide.  If, 
however,  5-bromuracil  is  treated  with  bromine  water  it  is  con- 
verted back  again  into  dibromoxyhydrouracil.  Picric  acid  inter- 
feres with  the  color  and  should  be  removed  before  applying  the 
test. 

— — . 

Dibromoxyhydrouracil,    HN — CO 


HN— CHOH 

In  preparing  this  compound  for  use  in  further  experiments  we 
usually  took  5  grams  of  uracil,  suspended  in  20  cc.  of  water,  and 
added  a  little  over  15  grams  of  bromine.  The  uracil  dissolved 
completely  on  warming,  and,  on  cooling,  a  crystalline  mass  sepa- 
rated. The  material  thus  obtained  had  a  yellow  color  from 
excess  of  bromine,  and  the  yield  that  first  separated  was  almost 
90  per  cent  of  the  calculated.  On  crystallizing  once  from  water 
colorless,  large,  flat  prisms  or  blocks  separated.  The  habit  of 
these  crystals  is  shown  in  the  microphotographs  (magnified  60 
times)  Plate  II. 

The  same  substance  was  obtained  when  0.6  gram  of  cytosin  sul- 
phate was  suspended  in  water  and  bromine  added  until  the  salt 
dissolved.  The  solution  was  then  concentrated  to  a  small  volume 
and  cooled.  The  prisms  obtained  melted  at  205-6°  C.  (Analy- 
sis (III). 

The  analytical  results  were  as  follows: 

Calculated  for  Found: 

C4H4O3N2Br2:  I.  II.  III.  IV. 

N 9.72  9.59  9.63  9.46 

Br 55.55  56.00 

Dibromoxyhydrouracil  melts  with  effervescence  at  203-6°. 
It  shows  signs  of  decomposition  below  this  temperature.  It  is 
more  soluble  in  water  than  uracil.  The  solution  of  the  pure 
white  crystals  is  neutral  to  litmus,  but  on  boiling  it  has  an  acid 
reaction  and  finally  5-bromuracil  separates.  In  accordance  with 
this  silver  nitrate  gives  no  precipitate  in  the  cold  but  on  warming 
with  this  reagent  silver  bromide  separates. 

1  Wheeler  and  Merriam:  Amer.  Chem.  Journ.,  xxix,  p.  486,  1903. 


1 88  Color  Test  for  Uracil  and  Cytosin 

Dibromoxyhydrouracil  dissolves  readily  in  alcohol.  If  boiled 
with  alcohol  5-bromuracil  separates.  If  the  alcoholic  solution  is 
treated  with  a  solution  of  sodium  in  alcohol  a  purple  percipitate 
is  at  once  produced  similar  to  the  barium  hydroxide  percipitate. 
Alcoholic  potassium  hydroxide  also  produces  a  similar  colored 
precipitate.  These  colored  alkali  salts  differ  from  the  barium 
hydroxide  precipitate  by  being  instantly  decomposed  and  decol- 
orized by  treatment  with  water.  The  aqueous  solution  then 
turns  green  and  finally  orange  on  standing. 

Aqueous  ammonia  immediately  dissolves  the  dibrom-deriva- 
tive,  and  removes  bromine;  the  solution  slowly  takes  on  yellow, 
then  a  garnet  color  and  if  sufficient  material  is  present  a  reddish- 
brown  precipitate  separates. 

Dibromoxyhydrouracil  is  almost  insoluble  in  ether. 

THE    PURPLE    PRECIPITATE. 

The  precipitate  produced  by  adding  barium  hydroxide  to  an 
aqueous  solution  of  dibromoxyhydrouracil  when  exposed  on 
paper  to  dry  in  the  air  turned  red.  When  treated  with  acetic 
acid  it  changed  to  a  bright  red  powder,  while  the  precipitate  when 
freshly  precipitated  dissolved  completely  in  acetic  acid.  The 
analysis  of  the  precipitate  was  therefore  abandoned.  It  was 
shown  that  the  substance  yields  alloxantin  on  treatment  with 
acids  as  follows:  Four  and  a  half  grams  of  dibromoxyhydro- 
uracil were  dissolved  in  40  cc.  of  water  and  added  to  1 1  grams  of 
crystallized  barium  hydroxide  in  100  cc.  of  water.  The  purple 
precipitate  was  rapidly  filtered  but  no  attempt  was  made  to  wash 
it.  It  was  immediately  dissolved  in  dilute  hydrochloric  acid  and 
the  barium  was  removed  by  adding  20  per  cent  of  sulphuric  acid. 
The  colorless  solution,  which  on  testing  a  portion  with  barium 
hydroxide  again  gave  a  purple  precipitate,  was  allowed  to  evapo- 
rate in  a  desiccator.  On  standing  over  night  it  gave  small, 
stout,  colorless  transparent  prisms.  These  melted  at  243°  C.  with 
effervescence.  Behrendand  Friedrich1  state  that  alloxantin  melts 
at  243—5°.  This  material  was  not  dialuric  acid  since  its  aqueous 
solution  failed  to  decompose  carbonate  of  sodium  and  it  was  not 

1  Ann.  d.  Chem.  (Liebig),  cccxliv,  p.  n,  1906. 


Henry  L.  Wheeler  and  Treat  B.  Johnson       189 

isodialuric  acid  because  it  melted  over  100°  higher.     A  nitrogen 
determination  agreed  with  the  calculated  for  alloxantin : 

Calculated  for 

C8H6O8N4  +  2H20:  Found: 

N 17.40  percent,  17 .  n  per  cent. 

6-Aminopyrimidin,     N=C  —  NH2 

I  I 
HC     CH 

II  II 
N— CH 

One  gram  of  2-chlor-6-aminopyrimidin  was  dissolved  in  20  cc. 
of  colorless,  concentrated  hydriodic  acid  and  then  evaporated  to 
dryness  on  the  water  bath.  Iodine  separated  in  abundance. 
The  residue  was  evaporated  several  times  with  a  solution  of  sul- 
phur dioxide.  The  colorless  solution  was  then  treated  with  an 
excess  of  silver  sulphate,  filtered  and  the  silver  was  then  removed 
with  hydrogen  sulphide.  On  concentrating  the  solution  a  syrup 
was  obtained,  which,  when  taken  up  in  boiling  alcohol,  gave  well- 
crystallized  colorless  prisms.  The  yield  was  over  0.8  gram.  The 
crystals  melted  at  143°  to  clear  oil,  and  nitrogen  determinations 
agreed  with  the  calculated  for  an  acid  sulphate  of  6-amino- 
pyrimidin. 

Calculated  for  Found: 

C4HSN3.H2S04:  I.  II. 

N 21.76  2I-55  21. ii 

The  solution  of  this  material  was  freed  from  sulphuric  acid  by 
means  of  barium  hydroxide  and  the  excess  of  barium  hydroxide 
was  removed  with  carbonic  acid.  The  free  base  proved  to  be 
extremely  soluble  in  water.  The  aqueous  solution  was  precipi- 
tated by  phosphotungstic  and  picric  acid,  and  it  gave  a  precipi- 
tate of  silver  salt  when  treated  with  silver  nitrate  in  neutral  solu- 
tion. This  precipitate  was  soluble  in  ammonia.  With  bromine 
water  and  barium  hydroxide  it  gave  no  color. 


V.     RESEARCHES  ON  PYRIMIDINS:   ON  SOME  SALTS  OF 

CYTOSIN,  ISOCYTOSIN,  6-AMINOPYRIMIDIN 

AND  6-OXYPYRIMIDIN. 

(Twenty-second  Paper.) 
BY  HENRY  L.  WHEELER. 

(From  the  Sheffield  Laboratory  of  Yale  University.) 
(Received  for  publication,  June  10,  1907.) 

It  has  been  shown  by  Richard  Burian1  when  guanin  (I) ,  mixed 
with  carbohydrates,  is  heated  with  30-40  per  cent  sulphuric  acid 
that  hydrolysis  and  reduction  take  place  at  the  same  time,  the 
imidazole  group  is  removed  and  isocytosin2  (II)  and  uracil  (IV) 
result.  It  may  be  added  that  the  probable  formation  and 
decomposition  of  xanthin  (III)  would  also  give  uracil.  This 
decomposition  of  guanin  may  be  represented  as  follows: 


HN—  CO 

I       I 
H2N—  C      C—  NH< 


N—  C 

I 

1 
HN—  CO 

I        I 


N— CH 
II 


CH 


HN— CO 

I        I 
OC      C— NH\ 

I       II 
HN— C— 

III 

I 
HN— CO 

I 
OC      CH 

I       II 
HN— CH 

IV 


CH 


When  adenin  (V)  was  treated  in  a  similar  manner,  Burian 
obtained  6-aminopyrimidin  (VI),  while  6-oxypyrimidin  (VIII), 
which  would  be  expected  to  result  in  this  case  both  by  the 


1  Asher-Spiro :  Ergeb.  d.  Physiol.,  v,  p.  795,  1905. 

2  Wheeler  and  Johnson:  Anter.  Chem.  Journ.,  xxix,  p.  492,  1903. 

285 


286  Researches  on  Pyrimidins 

decomposition  of  hypoxanthin  (VII)  and  by  the  hydrolysis  of 
6-aminopyrimidin,  escaped  detection.1 

N=C— NH2  HN— CO 

II  II 

HC     C— NHx  >         HC     C— NH\ 

II       II  /CH  ||       ||  )CH 

N— C—    N/  N— C—     N/ 

V  VII 

1  1 

N=C— NH2  HN— CO 

II  II 

HC     CH  >         HC     CH 

II       II  II       II 

N— CH  N— CH 

VI  VIII 

The  three  pyrimidin  bases,  isocytosin,  6-aminopyrimidin  and 
6-oxypyrimidin,  are  probably  formed  in  the  energetic  hydrolysis 
of  the  nucleic  acids  by  sulphuric  acid  and,  since  it  has  now  been 
found  that  the  general  reagents  which  precipitate  cytosin  also 
precipitate  these  bases,  an  examination  of  the  properties  of  the 
compounds  and  some  of  their  salts  was  undertaken,  along  with 
the  similar  ones  of  cytosin.  The  statement  of  Burian  that  6- 
aminopyrimidin  and  isocytosin  according  to  their  entire  behavior 
must  obstinately  adhere  to  cytosin  ("dem  sie  ihrem  ganzen  Ver- 
halten  nach  hartnackig  anhaften  mussten")  has  been  found  to 
be  more  especially  true  in  the  case  of  isocytosin. 

Of  the  three  bases  6-oxypyrimidin  is  new.  Isocytosin  was 
first  prepared  synthetically  in  this  laboratory2  and  later  it  was 
obtained  in  a  different  manner  by  Gabriel  and  Colman.3 

In  the  case  of  6-aminopyrimidin,  Burian  states  that  the  base 
was  isolated  in  the  form  of  the  silver  salt,  by  precipitating  in 
neutral  solution  with  silver  nitrate.  This  was  decomposed  by 
means  of  hydrogen  sulphide  and  the  base  precipitated  by  phos- 
photungstic  acid.  A  solution  of  the  free  base  was  then  obtained 
in  the  usual  manner  from  which  he  prepared  and  analyzed  the 

1  In   an   article   published  while   this   paper  was  in  press  (Zeitschr.  f. 
physiol.  Ghent.,  li,  p.  444,  1907),  Burian  describes  the  isolation  of  6-oxy- 
pyrimidin. 

2  Loc.  cit. 

3  Ber.  d.  deutsch.  chem.  Gesellsch.,  xxxvi,  p.  3382,  1903. 


Henry  L.  Wheeler  287 

picrate  and  chloroplatinate.  He  says  nothing  further  in  regard 
to  the  base  or  its  salts. 

6-Aminopyrimidin,  however,  was  first  prepared  by  Ernst  Biitt- 
ner,  who  obtained  it  from  barbituric  acid  by  means  of  a  series  of 
operations.1  This  author  described  the  free  base  and  he  pre- 
pared the  hydrochloride,  easily  soluble  rhombic  tables;  the  chloro- 
platinate and  picrate,  needles,  difficultly  soluble.  Our  knowl- 
edge of  these  pyrimidins  stood  at  this  point  when  the  following 
work  was  begun. 

It  has  now  been  found  that  6-oxypyrimidin  is  formed  when 
2-thiouracil  (IX),  which  can  be  easily  prepared2  in  any  desired 
quantity,  is  treated  with  hydrogen  dioxide. 

HN— CO  HN— CO 

II  II 

SC     CH+3O+H2O  =      HC     CH  +  H2SO4 

I       II  II      II 

HN— CH  N— CH 

IX 

The  writer  finds,  however,  that  6-oxypyrimidin  is  more 
smoothly  obtained  by  warming  2,  6-dichlorpyrimidin  (X),  pre- 
pared from  uracil3  or  2-thiouracil,4  with  hydriodic  acid  and  red 
phosphorus.  The  hydrogen  iodide  salt  results  from  which  the 
pure  base  can  be  obtained  in  the  usual  manner. 

N=CC1  HN — CO 

I  I  I 

C1C     CH+3HI+H20=    HC     CH.HI+I2+2HC1 

II  II  II      II 
N— CH                                N— CH 

~  X 

The  6-aminopyrimidin  used  in  this  work  was  prepared  by  a 
shorter  and  more  convenient  method  than  the  one  employed  by 
Biittner  mentioned  above.  2,  6-Dichlorpyrimidin5  was  heated 

1  Ber.  d.  deutsch.  chem.  Gesellsch.,  xxxvi,  p.  2232,  1903. 

2  Wheeler  and  Bristol:  Amer.  Chem.  Journ.,  xxxiii,  p.  458,  1905. 

3  Gabriel:  Ber.  d.  deutsch.  chem.  Gesellsch.,  xxxviii,  p.  1690,  1905. 

4  Johnson  and  Menge:  This  Journal,  ii,  p.  114,  1906. 

5  Care  should  be  taken  in  working  with  2,  6-dichlorpyrimidin  not  to 
expose  the  material  to  the  skin,  since  it  has  a  very  corrosive  action.     In 
one  case  deep  and  painful  blisters  were  formed  on  the  hands,  resembling 
those  produced  by  hydrofluoric  acid. 


288  Researches  on  Pyrimidins 

with  alcoholic  ammonia.  This  gave  a  mixture  of  2-amino-6- 
chlorpyrimidin  (XI)  and  2-chlor-6-aminopyrimidin  (XII).1  It 
was  found,  on  boiling  this  mixture  with  water  and  zinc  dust, 
that  2-amino-6-chlorpyrimidin  was  reduced  to  the  very  soluble 
2-aminopyrimidin2  which  could  easily  be  removed,  while  2-chlor- 
6-ammopyrimidin  remained  unaltered.  The  pure  2-chlor-6- 
aminopyrimidin  then  on  warming  on  the  steam-bath  with  hydri- 
odic  acid  was  smoothly  reduced  and  the  hydrogen  iodide  salt  of 
6-aminopyrimidin  was  obtained.  Although  Biittner  worked 
with  small  quantities  of  this  base  (0.25  gram)  his  results  and 
the  writer's  agree  in  every  respect. 

N=CC1  N=C— NH2  N=C— NH2 

II  II 

H2N— C     CH  C1C     CH >      HC     CH 

II       II  II       II  II      II 

N— CH  N— CH  N— CH 

XI  XII 

EXPERIMENTAL    PART. 

6-Oxypyrimidin,  HN — CO 

I  I 
HC     CH 

II  II 
N— CH 

Thirteen  grams  of  2, 6-dichlorpyrimidin  were  slowly  added 
to  50  cc.  of  concentrated  hydriodic  acid  and  6  grams  of  red 
phosphorus  on  the  steam -bath.  As  soon  as  all  was  added  the 
mixture  was  boiled  for  a  few  minutes  and  then  the  hydrogen 
iodide  was  removed,  as  far  as  possible,  by  evaporation  in  a 
vacuum  at  100°.  The  residue  on  taking  up  in  hot  water  and 
filtering  from  red  phosphorus  formed  a  syrup,  which  deposited 
well  crystallized  needles,  decomposing  with  effervescence  when 
kept  at  300°  (6-oxypyrimidin  hydriodide).  The  whole  was  dis- 
solved in  water  and  an  excess  of  silver  sulphate  was  added  and 
filtered,  the  filtrate  was  precipitated  with  hydrogen  sulphide, 
the  phosphoric  and  sulphuric  acids  removed  by  means  of  barium 

1  Gabriel :  Loc.  tit. 
2Bftttner:  Loc.  tit. 


Henry  L.  Wheeler  289 

hydroxide,  and  then,  on  removing  the  excess  of  barium  with 
carbon  dioxide  and  evaporating  to  dryness,  a  very  soluble 
crystalline  cake  was  obtained.  This  weighed  5.6  grams.  On 
crystallizing  from  ethyl  acetate  beautiful,  long,  thin,  prismatic 
needles  separated  melting  to  a  clear  oil  at  164°- 165°.  The  per 
cent  of  nitrogen  in  this  material  agreed  with  the  calculated 
for  6-oxypyrimidin  (Analysis  I  and  II). 

The  same  compound  was  also  obtained  as  follows:  Twenty 
grams  of  2-thiouracil  were  suspended  in  a  liter  of  hot  water  and 
about  530  cc.  of  commercial  hydrogen  dioxide  solution  were 
added  in  portions.  The  thiouracil  dissolved  and  after  boiling  a 
few  minutes,  sulphur  dioxide  was  added  and  the  solution  was 
evaporated  to  a  convenient  volume.  The  sulphuric  acid,  which 
had  been  formed  in  the  reaction,  was  removed  by  means  of  an 
excess  of  barium  hydroxide  and  the  excess  of  the  latter  was  pre- 
cipitated with  carbon  dioxide.  The  solution  was  then  evapor- 
ated to  dryness  and  the  residue  was  extracted  with  boiling  alco- 
hol. This  dissolved  the  6-oxypyrimidin,  leaving  a  mixture  weigh- 
ing about  7 . 7  grams  of  uracil  and  a  barium  salt  of  an  organic  acid 
that  was  not  further  examined.  The  barium  salt  was  insoluble 
in  alcohol  but  readily  soluble  in  water,  it  had  the  peculiar  prop- 
erty of  swelling  up  to  many  times  its  original  volume  when 
heated  on  platinum  foil. 

The  alcoholic  solution  was  evaporated  to  dryness  and  the 
residue  extracted  with  ethyl  acetate.  This  gave  about  6  grams 
of  crude  6-oxypyrimidin.  When  crystallized  from  a  large 
amount  of  benzene  it  formed  colorless  needles  melting  less  sharply 
than  the  above  preparation  (Analysis  III).  All  the  nitrogen 
determinations  in  this  paper  were  made  by  Kjeldahl's  method. 

Calculated  for  Found: 

C4H4ON2:  I.  II.  III. 

N  ....       29.16  29.02  28.78  28.85 

6-Oxypyrimidin  is  insoluble  in  petroleum  ether,  very  diffi- 
cultly soluble  in  ether,  somewhat  more  soluble  in  hot  benzene 
and  still  more  soluble  in  ethyl  acetate.  This  solvent  is  the  best 
to  use  to  extract  and  crystallize  the  material.  It  is  extremely 
soluble  in  water  and  alcohol,  and,  in  this  respect,  like  6-amino- 
pyrimidin  could  not  possibly  be  mistaken  for  the  far  more  insolu- 
ble cytosin  and  isocytosin. 


290  Researches  on  Pyrimidins 

This  monooxypyrimidin  unlike  the  dioxypyrimidin  (uracil) 
gives  no  color  with  bromine  and  barium  hydroxide. 

It  is  precipitated  by  phosphotungstic  acid,  and,  in  neutral 
solution,  by  silver  nitrate  or  mercuric  chloride.  A  strong  solu- 
tion is  precipitated  by  picric  acid  and  also  by  hydrochloro- 
platinic  acid.  The  platinum  chloride  double  salt  separates 
slowly  and  forms  prisms.  It  did  not  have  a  definite  melting  or 
decomposing  point. 

6-Aminopyrimidin,  N=C — NH2 

I  I 
HC     CH 

II  II 
N— CH 

2-Chlor-6-aminopyrimidin  reduces  smoothly  to  6-aminopyri- 
midin  when  warmed  on  the  water-bath  with  concentrated 
hydriodic  acid  and  red  phosphorous.1  The  residue,  after  the 
removal  of  hydrogen  iodide  by  evaporation  was  treated  with 
silver  sulphate,  barium  hydroxide,  etc.,  as  in  the  case  of  6-oxy- 
pyrimidin,  for  the  preparation  of  the  free  base.  It  was  found 
that  2 . 7  grams  of  2-chlor-6-aminopyrimidin,  27  cc.of  concentrated 
hydriodic  acid  and  an  excess  of  red  phosphorus  gave  1.6  gram 
of  crude  base  while  the  calculated  is  1.9  gram.  When  crystal- 
lized from  ethyl  acetate,  snow  white  clusters  of  thin,  leaf -like 
crystals  separated.  The  appearance  of  these  clusters  was  similar 
to  those  of  6-oxypyrimidin.  The  material  melted  at  i5i°-i52°. 
Buttner2  gives  the  same  melting  point  for  this  base.  It  is  ex- 
tremely soluble  in  water  and  alcohol  and  it  is  precipitated  in 
more  dilute  solutions  by  the  same  reagents  which  precipitate 
6-oxypyrimidin. 

The  Acetyl  Compounds. 

A  peculiar  acetyl  derivative  of  6-oxypyrimidin  was  formed 
when  the  base  was  dissolved  in  acetic  anhydride  and  evaporated 
to  dryness  on  the  steam-bath.  When  the  residue  was  crystal- 
lized from  alcohol,  in  which  it  is  quite  soluble,  it  formed  colorless 
needles  or  spikes.  It  is  sharply  distinguished  from  the  other 

1  Wheeler  and  Johnson:  This  Journal,  iii,  p.  186,  1907. 

2  Loc.  cit. 


Henry  L.  Wheeler  291 

acetyl  compounds  by  having  two  melting  points.  When  heated 
rapidly  it  melted  to  a  clear  oil  at  180°,  or  a  little  below,  then  if 
the  temperature  was  kept  at  this  point  it  solidified  and  on  further 
heating  it  remelted  with  effervescence  at  2i5°-22o°.  (Analysis 
I  and  II.) 

Another  sample  of  the  acetyl  compound  was  prepared  and  crys- 
tallized from  water.  It  then  separated  in  the  form  of  prismatic 
scales  which  had  the  same  behavior  on  heating  as  the  above.  It 
was  dried  at  5o°-55°. 

(Analysis  III.)  The  analytical  results  are  low  for  a  simple 
acetyl  derivative,  but  they  agree  with  the  calculated  for  the 
expected  acetyl  compound  with  a  molecule  of  water  of  crystalliza- 
tion, or,  if  water  of  constitution,  equally  well  for  acetylformami- 
dine  acrylic  acid,  CH3CONH-CH  =N-CH  =CHCOOH,  or  sim- 
ply an  acetic  acid  salt  of  6-oxypyrimidin.  The  latter,  however, 
is  excluded  since  the  free  base  dissolves  in  glacial  acetic  acid 
and  on  evaporation  is  recovered  unaltered. 

In  order  to  determine  whether  the  compound  has  water  of 
crystallization  or  water  of  constitution,  a  portion  of  the  material, 
which  had  been  crystallized  from  water,  was  heated  at  109°— 115° 
for  three  hours.  It  then  lost  4  per  cent  in  weight  This  was  due, 
not  to  the  fact  that  water  was  given  off  but  that  the  substance 
volatilized,  since  a  nitrogen  determination,  after  heating,  gave 
the  same  result  as  in  the  case  of  the  previous  determinations 
(Analysis  IV) .  This  result  makes  it  appear  improbable  that  the 
substance  has  water  of  crystallization.  The  view  that  the  com- 
pound is  acetylformamidine  acrylic  acid,  therefore,  remains  at 
present  as  most  probable.  This,  however,  must  be  left  for  future 
work  to  decide. 

Calculated  for  Found: 

C6H8O3N2:  I.  II.  III.  IV. 

N 17.94  17.75  17.64  17.88  17.86 

Acetyl-6-aminopyrimidin. — A  quarter  of  a  gram  of  the  pure 
base  was  dissolved  in  acetic  anhydride  and  heated  to  boiling,  then 
evaporated  to  dryness  on  the  steam-bath  When  crystallized 
from  about  5  cc.  of  water  it  formed  an  asbestos-like  mass  of  fine 
needles.  About  0.2  gram  separated.  It  melted  at  202°,  to  a 
clear  oil,  without  effervescence.  Analysis: 

Calculated  for 

C6H7ON3:  Found: 

N 30.43  30.35 


292  Researches  on  Pyrimidins 

The  Pier  ate  s. 

The  picrate  of  6-oxypyrimidin  is  far  more  soluble  than  the 
picrates  of  cytosin  and  isocytosin.  It  also  differs  decidedly  in 
appearance  from  these  salts.  6-Aminopyrimidin  picrate,  on  the 
other  hand,  closely  resembles  cytosin  picrate  both  in  regard  to 
solubility  and  crystalline  form.  The  presence  of  this  picrate 
is  possibly  the  cause  of  the  picrate  of  cytosin  from  natural  sources 
invariably  melting  lower  than  that  of  synthetic  cytosin.1 

6-Oxypyrimidin  Picrate. — A  saturated  aqueous  solution  of 
picric  acid  was  mixed  with  a  moderately  strong  solution  of  6- 
oxypyrimidin ;  as  no  precipitate  was  formed  the  solution  was  con- 
centrated to  almost  the  volume  of  picric  acid  solution  employed. 
On  standing  a  long,  flat,  fern-like  growth  of  crystals  separated. 
It  melted  to  a  clear  oil  at  190°.  Analysis: 

Calculated  for 
CioH7O9N5:  Found: 

N 21.53  21.55 

6-Aminopyrimidin  Picrate. — Forty  cc.  of  picric  acid  solution 
were  added  to  0.2  gram  of  6-aminopyrimidin  in  a  little  water.  A 
bulky  precipitate  was  formed  at  once  which  dissolved  on  adding 
40  cc.  of  water  and  then  boiling.  On  cooling,  long  bright,  yel- 
low, hair-like  needles  separated.  On  heating  these  showed  evi- 
dence of  change  a  little  below  200°  and  then  suddenly  melted 
at  226°  to  a  clear  oil.  This  then  turned  brown  and  vigorously 
effervesced  at  270°— 280°.  Analysis: 

Calculated  for  Found: 

C10H807N6:  I.  II. 

N  25.92  25.76  25.92 

The  Hydrochlorides. 

The  hydrochlorides  of  6-oxypyrimidin,  6-aminopyrimidin  and 
of  isocytosin  are  even  more  soluble  than  the  easily  soluble  cyto- 
sin hydrochloride.  The  latter  and  6-oxypyrimidin  hydrochlor- 
ide  separate  with  water  of  crystallization.  The  hydrochlorides 
are  difficultly  soluble  in  alcohol. 

6-Oxypyrimidin  Hydrochloride,  C4H4ON2.HC1.H2O. — Pure  6-oxy- 
pyrmidin  was  dissolved  in  dilute  hydrochloric  acid  and  evapo- 
rated to  dryness  on  the  steam -bath.  The  residue  formed  a  syrup 

1  Amer.  Chem.  Journ.,  xxix,  pp.  494,  500,  505,  1903. 


Henry  L.  Wheeler  293 

which  solidified  on  cooling.  It  was  dissolved  in  water  and  allowed 
to  crystallize  by  standing  over  sulphuric  acid.  Thick  transparent 
prisms  or  oblong  blocks  separated  some  10-15  millimeters  in 
length.  These  melted  partially  below  100°,  finally  melting  to 
an  oil  at  about  205°-2io°.  Analysis: 

Calculated  for  Found: 

C4H7O2N2C1:  I.  II. 

N  18.60  18.54  18.64 

A  water  determination  was  made  by  heating  the  material  at 
114°  for  one  hour.  This  gave  13.1  per  cent  while  the  calculated 
is  11.96.  When  reheated  at  120°  it  was  found  that  the  material 
slowly  volatilized,  which  explains  the  high  result. 

6-Aminopyrimidin  Hydro  chloride,  C4H5N3.HC1. — The  base  was 
evaporated  to  dry  ness  with  hydrochloric  acid.  The  material 
was  then  taken  up  in  a  little  water  and  left  to  crystallize  in  a 
desiccator.  Transparent  prisms  or  tables  separated  from  the 
syrupy  solution.  When  dried  over  calcium  chloride  they  melted 
to  an  oil  at  257°  and  then  effervesced.  A  nitrogen  determination 
showed  that  the  salt  was  anhydrous. 

Calculated  for 
C4H5N3.HC1:  Found: 

X 31.93  31.49 

Isocytosin  Hydrochloride ,  C4H5ON3.HCL— This  salt  has  a  de- 
cided tendency  to  crawl  up  the  sides  of  a  dish  when  left  to 
crystallize.  The  crystals  which  separate  in  this  manner  are 
prisms,  when  precipitated  from  an  aqueous  solution  by  the  addi- 
tion of  alcohol  it  forms  little  square  tables  or  blocks.  When 
heated  it  begins  to  change  in  appearance  at  about  250°  and  then 
effervesces  about  270°.  Analysis: 

Calculated  for 
C4H5ON3.HC1:  Found: 

N..  28.47  28.27 


Cytosin  Hydrochloride,  C4H5ON3.HC1.H2O.— If  cytosin  is  dis- 
solved in  strong  hydrochloric  acid  and  left  to  crystallize  in  a  des- 
iccator cytosin  dihydrochloride  is  obtained,  C^CN^HCl.1  If 
the  acid  solution  is  evaporated  to  dryness  and  the  residue  is 
taken  up  in  water  and  left  to  crystallize  spontaneously,  large, 
transparent  plates  separate  of  the  hydrous,  i :  i  salt.  This  salt 

1  Wheeler  and   Johnson:  Amer.  Chem.  Jottrn.,  xxxi,  p.  598,  1904. 


294  Researches  on  Pyrimidins 

loses  its  water  rapidly  at  50°  and  in  a  few  hours  on  exposure  to 
the  air.  It  differs  from  the  hydrous  6-oxypyrimidin  hydro- 
chloride  since  on  standing  over  night  the  crystals  become  entirely 
opaque.  It  is  more  soluble  than  the  dihydrochloride.  The  latter 
and  also  the  hydrous  cytosin  hydrochloride  both  melt  at  275°- 
279°.  Analysis: 

Calculated  for 
C4H5ON3.HC1.H2O:  Found: 

N 25.37  25.52 

Some  of  the  material  which  had  stood  for  about  3-4  hours  was 
dried  to  a  constant  weight  at  a  little  above  100°.  It  lost  9.5  per 
cent  of  water  while  the  calculated  for  one  molecule  of  water  is 
10.8  per  cent. 

The  Sulphates. 

The  sulphates  of  6-oxypyrimidin  and  6-aminopyrimidin  are 
very  soluble  in  water.  The  neutral  sulphate  of  isocytosin  is  less 
soluble  and  it  resembles  the  neutral  sulphate  of  cytosin  except 
that  it  does  not  crystallize  with  water.  The  three  sulphates 
which  cytosin  forms  have  been  prepared  and  some  new  facts  are 
given  for  their  identification.  The  sulphates  were  prepared  from 
the  hydrochlorides  by  treating  the  latter  with  an  excess  of  silver 
sulphate,  removing  the  excess  of  silver  by  means  of  hydrogen 
sulphide  and  then  evaporating.  Owing  to  their  solubility,  the 
sulphates  of  6-oxypyrimidin  and  6-aminopyrimidin  were  crys- 
tallized by  means  of  alcohol.  The  sulphates  of  isocytosin  and 
cytosin  were  allowed  to  crystallize  at  ordinary  temperatures  in 
order  to  determine  their  degree  of  hydration. 

6-Oxypyrimidin  Sulphate,  (C4H4ON2)2H2SO4. — This  salt  was 
purified  by  precipitating  the  strong  aqueous  solution  with  alcohol. 
After  the  fourth  precipitation  it  came  down  in  the  form  of  micro- 
scopic prisms  and  melted  with  effervescence  about  218°.  Analy- 
sis: 

Calculated  for  Found: 

C8H802N4.H2S04:  I.  II. 

N 19.31  19.29  19.32 

This  neutral  sulphate  also  separates  from  alcoholic  solutions 
containing  a  considerable  excess  of  sulphuric  acid. 


Henry  L.  Wheeler  295 

6-Aminopyrimidin  Sulphate,  C4H5N3.H2SO4,  was  described  in  a 
previous  paper.1 

Isocytosin  Sulphate,  (C4H5ON3)2H2SO4. — This  salt  separated 
from  the  aqueous  solution  containing  a  slight  excess  of  sulphuric 
acid,  on  standing,  in  the  form  of  balls  composed  of  radiating 
clusters  of  small  prisms.  It  melted  at  276°  with  effervescence. 
Analysis : 

Calculated  for  Found: 

C8HioO2Ne.H2SO4:  I.  II. 

N 26.25  26.30  25.98 

Basic  Cytosin  Sulphate,  (C4H5ON3)4H2SO4.2H2O.— This  hy- 
drous salt  has  frequently  been  obtained  by  Levene.2  It  was 
obtained  in  the  anhydrous  condition  by  Kossel  and  Steudel.3 
It  is  the  least  soluble  of  the  sulphates  mentioned  in  this  paper. 
It  has  the  highest  decomposing  point,  the  same  as  that  of  cyto- 
sin  itself,  namely,  323°.  It  was  obtained,  in  the  present  work, 
when  cytosin  monohydrochloride  was  treated  with  a  slight  excess 
of  silver  sulphate,  and  the  silver  then  removed  by  means  of  hydro- 
gen sulphide.  On  concentrating  the  solution  the  salt  separated 
in  the  form  of  sharply  defined,  long,  needle-like  prisms. 

Neutral  Cytosin  Sulphate,  (C4H5ON3)2H2SO4.2H2O.— The  anhy- 
drous form  of  this  salt  was  first  obtained  by  Levene,4  having 
dried  the  material  in  a  toluol  bath.  The  hydrous  form,  here 
described,  separated  on  allowing  the  mother  liquor  from  the 
above  basic  salt  to  evaporate  in  the  air.  Stouter,  more  compact 
masses  of  prisms  formed  which,  on  drying  in  the  air,  melted  with 
effervescence  at  287°.  Levene  found  290°.  The  analyses  now 
show  that  this  salt  crystallizes  with  two  molecules  of  water. 

Calculated  for  Found: 

C8Hi0O2N3.H2SO4.2H20:          I.  II.  III. 

N  23 . 59  23 . 66  23 . 45 

H2O  ....      10.11  10.13 

The  water  determination  was  made  by  heating  the  salt  at  1 18°- 
120°  for  an  hour. 

Acid  Cytosin  Sulphate,  C4H5ON3.H2SO4. — This  salt  has  been 
obtained  by  Kossel  and  Steudel ;  they  simply  mention  that  it  is 

1  Wheeler  and  Johnson:  This  Journal,  iii,  p.  189,  1907. 

2  Zeitschr.  f.  physiol.  Chem.,  xxxix,  pp.  7,  135,  481,  1903. 

3  Ibid.,  xxxviii,  p.  52,  1903. 

4  Ibid.,  xxxviii,  p.  81,  1903. 


296  Researches  on  Pyrimidins 

easily  soluble.1  It  is  easily  obtained  by  dissolving  the  neutral 
sulphate  in  20  per  cent  sulphuric  acid  and  allowing  the  material 
to  crystallize  in  a  desiccator.  The  stout,  transparent  crystals 
thus  obtained  appear  to  be  rhombohedrous.  These  have  the 
characteristic  property  of  becoming  opaque  when  an  attempt 
is  made  to  wash  them  with  water.  This  is  the  most  soluble 
sulphate  of  cytosin.  After  pressing  on  paper  and  drying  over 
calcium  chloride  the  material  melted  at  197°  to  a  colorless  oil. 
Analysis : 

Calculated  for  Found: 

C4H5ON3.H2S04:  I.  II. 

N 20.09  19.86  19.89 

Acid  Cytosin  Phosphate,  C4H5ON3.H3P04.— This  salt  was 
obtained  when  cytosin  monohydrochloride  (7  grams)  was  boiled 
with  phosphorous  oxychloride  (50  cc.)  for  two  hours.  The  phos- 
phorous oxychloride  was  then  evaporated  and  the  residue  treated 
with  ice.  The  material  dissolved  and,  evaporating,  a  syrup  was 
obtained  from  which  dilute  alcohol  precipitated  well  crystallized, 
long,  flat  prisms.  When  crystallized  from  water,  in  which  the 
salt  is  very  soluble,  it  melted  at  236°  with  effervescence.  Analy- 
sis: 

Calculated  for  Found: 

C4H5ON3.H3P04:  I.  II. 


20.09  20.09  19.95 


The  melting  or  effervescing  points  of  the  substances  com- 
pared in  this  work  are  given  in  the  following  table.  The  effer- 
vescing points  even  of  the  pure  compounds  may  vary  to  a  cer- 
tain amount,  perhaps  several  degrees,  according  to  the  rate  of 
heating,  amount  of  substance  used,  etc.  No  especial  accuracy 
is  claimed.  It  is  believed,  however,  that  the  melting  points  given 
will  be  found  to  be  sufficiently  constant  to  serve  as  an  aid  for 
the  identification  of  the  substances.  There  is  in  general  a  wide 
difference  in  the  melting  points  in  each  series.  This  should  be 
especially  serviceable  in  the  case  of  the  sulphates  of  cytosin. 

The  picrolonates  mentioned  in  the  table  are  the  most  insoluble 
salts  prepared.  Since  some  new  facts  have  been  observed  in  the 
case  of  picrolonates  these  salts  will  be  described  in  a  later  paper. 

1  Zeitschr.  f.  physiol.  Chem.,  xxxviii,  p.  52,  1903. 


Henry  L.  Wheeler 


297 


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CXLVL—  RESEARCHES   ON    PYRIMIDINES:    URACIL 
4-CARBOXYLIC  ACID. 

[TWENTY-THIRD  PAPER.] 

BY  HENRY  I,.  WHEELER. 

In  1897,  Miiller1  described  a  substance  obtained  by  con- 
densing oxalaceticethyl  ester  with  urea  by  means  of  hydrogen 
chloride  in  glacial  acetic  acid.  His  analytical  results  showed 
that  the  condensation  involved  the  separation  of  water  and 
alcohol,  and  he  represented  the  reaction  as  taking  place  with 
the  formation  of  uracil-4-ethylcarboxylate  as  follows : 

1  J.  prakt.  Chein.,  56,  488  (1897). 


NH2 
OC       + 


Researches  on  Pyrimidines. 
CO.OC2H5          HN  --  CO 
CH  ===    OC  CH 


359 


C2H5OH 


+ 


NH2       HOCCO.OC.jH5        HN 


OOC2H5       H2O 


I. 


There  is  nothing  in  Miiller's  article,  however,  to  show  that 
the  product  formed  was  a  pyrimidine.  The  condensation 
might  result  with  the  separation  of  water  and  alcohol  from 
the  oxalyl  radical;  the  process  would  then  be  represented  as 
follows  : 

NH2       COOC2H5 
OC       + 


NH2       COCH2COAH6 


HN- 
OC 
HN- 


C2H6OH 

f 
[6       H20 


II. 


An  acid  called  pyvureidic  acid  (Pyvureidsaure)  ,  correspond- 
ing to  this  ester,  has  been  recently  described  by  Gabriel,1  who 
obtained  it  by  treating  malyure'idic  acid  with  bromine. 

Formula  III.  has  been  assigned  by  Gabriel  to  pyvureidic 
acid  since  with  bromine  water  it  yields  dibrompyvurinic 
acid,  IV.,  the  same  substance  also  being  obtained  in  a  similar 
manner  from  brompyvureid,  V. 


HN- 

OC 

HN- 


H2N 


COOH 


=  CHC02H 


III. 


1  Ann.  Chem.  (Liebig),  348,  89  (1906). 


360  Wheeler. 

HN- 


Since  pyvureidic  acid  is  to  be  represented  by  formula  III., 
then  malyureidic  acid  has  the  five-membered  ring  structure, 
VI.,  given  to  it  by  Guareschi1  and  not  that  of  a  dihydrouracil- 
carboxylic  acid,  VII.,  as  represented  by  Grimaux.2 

HN  -  CO  HN  -  CO 

I  I 

OC  CH2 

HCH2CO2H  HN  --  CHCO2H 

VII. 

The  writer  has  prepared  Miiller's  ester  and  finds,  on  saponi- 
fication,  that  it  gives  an  acid  isomeric,  and  not  identical,  with 
Gabriel's  pyvureidic  acid.  The  action  of  bromine  water  on 
this  acid  shows  that  the  substance  is  a  pyrimidine.  This  was 
tried,  following  the  directions  given  by  Gabriel  in  the  case  of 
pyvureidic  acid.  The  acid  dissolved,  carbon  dioxide  was 
evolved  and,  on  evaporating  the  solution,  large  crystals  of 
dibrombarbituric  acid  separated.  The  reaction  can  be  repre- 
sented as  follows  : 

HN  --  CO 

I  I 

OC  CH         +  H2O  4  6Br    = 

I  ii 

HN  --  CC02H 


4HBr. 


This  proves  that  the  acid  in  question  is  uracil-4-carboxylic 

1  Ber.  d.  chem.  Ges.,  10,  1748  (1877). 

*  Jahres.  d.  Chem.,  1876,  p.  752.      Ann.  chim.  phys.   fs],  11,  413   (1877).      Bull. 
Soc.  Chim.  [2],  24,  337  (1875). 


Researches  on  Pyrimidines.  361 

acid  and  that  Miiller's  ester  has  the  pyrimidine  structure,  I., 
originally  assigned  to  it.  It  also  confirms  Gabriel's  conclu- 
sions that  pyvureidic  and  malyureidic  acids  are  not  pyrimi- 
dines. 

Uracil-4-carboxylic  acid  has  its  carboxyl  group  much  more 
firmly  bound  than  the  isomeric  uracil-5-carboxylic  acid.  It 
is  not  converted  into  uracil  when  heated  with  20  per  cent 
sulphuric  acid  at  200°,  while  the  isomeric  5-derivative  readily 
yields  uracil  on  heating  with  acids.1  This  excludes  the  possi- 
bility that  uracil  exists  in  the  nucleic  acids  as  a  4-carboxyl 
derivative.  Unlike  the  isomeric  pyvureidic  acid,  uracil-4- 
carboxylic  acid  crystallizes  with  i  molecule  of  water  of  crys- 
tallization. The  hydrous  acid  has  the  empirical  formula  of 
orotic  acid,  but  its  melting  point  is  different.  The  melting 
point  of  its  methyl  and  ethyl  esters  also  differ  from  those  of 
the  corresponding  esters  of  orotic  acid. 

The  yield  of  uracil-4-ethylcarboxylate,  by  Miiller's  method, 
is  only  about  20  per  cent  of  the  calculated,  and  attempts  were 
made  to  prepare  it  by  treating  ethylpseudothiourea  hydro- 
bromide  in  alkaline  solution  with  oxalaceticethyl  ester.  This 
gave  no  pyrimidine,  but  instead  a  pseudourea  addition  product 
or  salt.  Owing  to  the  poor  yield  of  this  product,  no  attempt 
was  made  to  convert  it  into  the  pyrimidine  by  heating,  as  has 
been  found  to  prove  successful  by  Gabriel  and  Colman  in  the 
case  of  the  analogous  addition  product  of  anisamidine  and 
acetylacetone.2  In  this  connection,  and  in  regard  to  the 
limits  of  our  general  method  for  the  preparation  of  pyrimi- 
dines,  it  is  interesting  to  note  that  such  acid  molecules  as 
acetylethylcyanacetate,  CH3COCH(CN)CO2C2H5,  and  oxal- 
malonic  ethyl  ester,  C2H5OCOCOCH(CO2C2H5)2,  also  failed 
to  condense  with  the  pseudourea,  but  like  oxalacetic  ethyl 
ester,  formed  addition  products.  On  the  other  hand,  Dr. 
Johnson  has  found  that  oxalpropionic  ester, 

C2H5OCOCOCH(CH3)CO2C2H5, 

condenses  normally  in  alkaline  solution,  giving  2-mercapto-4- 
carbethoxy-5-methyl-6-oxypyrimidine. 

1  THIS  JOURNAL,  37,  392  (1907). 

1  Ber.  d.  chem.  Ges.,  32,  1529  (1899). 


362  Wheeler. 

Ruhemann  and  Staple  ton1  found  that  ethyl  acetylenedicar- 
boxylate,  C2H5OCOC=CCOOC2H5,  condenses  with  guanidine 
to  form  2-amino-6-oxy-4-ethylcarboxylate;  whether  uracil- 
4-carboyxlic  acid  can  be  prepared  more  readily  from  this 
substance  than  by  the  above  method,  or,  by  the  condensation 
of  the  acetylene  ester  with  a  urea  derivative,  must  be  left  for 
future  work  to  decide. 

EXPERIMENTAL   PART. 

HN CO 

I       I 

Uracil-4-carboxylic  Acid,  OC  CH  .— Miiller's 

I  II 

HN CCOOH.H20 

"  Uracilcarbonsaureathylester  "  was  prepared  according  to  his 
directions.2  It  was  found  that  18  grams  of  oxalacetic  ethyl 
ester,  after  2  weeks,  gave  a  little  over  4  grams  of  uracil-4- 
ethylcarboxylate  and  that  60  grams  of  oxalacetic  ethyl  ester 
gave  about  12  grams  of  the  crude  pyrimidine. 

The  ester  was  saponified  as  follows:  Five  grams  were  dis- 
solved in  about  60  cc.  of  hot  alcohol  and  twice  the  calculated 
amount  of  potassium  hydroxide  (3  grams)  in  10  cc.  of  water, 
was  added ;  the  whole  then  solidified  to  a  thick  mass.  A  clear 
solution  was  obtained  by  adding  about  150  cc.  of  water.  This 
was  then  evaporated  to  a  small  volume  and  the  acid  was  pre- 
cipitated by  adding  dilute  hydrochloric  acid  in  excess.  The 
yield  was  near  the  calculated.  The  acid  is  very  difficultly 
soluble  in  alcohol.  It  was  purified  for  analysis  by  crystal- 
lizing from  water.  It  is  moderately  soluble  in  hot  water, 
difficultly  soluble  in  cold,  and  it  separates  in  the  form  of  micro- 
scopic, stout,  twinned  prisms,  some  in  the  form  of  a  cross. 

0.6929  gram  substance  lost  0.0712  gram  of  water  when  heated 
i  hour  at  I25°-I3O°. 

Calculated  for 
C5H4O4N2.H2O.  Found. 

H2O  10.34  10.26 

N  16.09  16.12 

1  J.  Chem.  Soc.  Proc.,  16,  121  (1900). 

2  J.  prakt.  Chem.,  56,  488  (1897). 


Researches  on  Pyrimidines.  363 

The  acid  usually  melts  at  347  °  with  strong  effervescence ;  oc- 
casionally samples  were  obtained  which  decomposed  on  heat- 
ing without  effervescence.  It  gives  a  white,  amorphous  pre- 
cipitate with  silver  nitrate,  soluble  in  nitric  acid.  The  aqueous 
solution  gives  a  crystalline  precipitate  with  barium  chloride. 
When  heated  (0.5  gram)  with  20  per  cent  sulphuric  acid  (5  cc.) 
at  i85°-2o8°,  for  2  hours,  no  uracil  was  formed.  A  portion 
of  the  solution  was  tested  with  bromine  water  and  barium 
hydroxide1  for  uracil,  but  no  color  whatever  was  obtained. 
Therefore,  there  could  not  have  been  as  much  as  0.005  gram 
of  uracil  formed.  The  material  remaining  was  crystallized 
from  water,  whereupon  it  melted  at  347°  with  vigorous  effer- 
vescence. 

It  was  found  that  the  acid  (0.5  gram)  was  not  attacked  by 
fuming  nitric  acid  (10  cc.)  when  boiled  and  then  evaporated 
to  dryness  on  the  water-bath.  The  operation  was  repeated 
with  20  cc.  of  fuming  nitric  acid.  There  sidue  then,  when  crys- 
tallized from  water,  melted  with  effervescence  at  347°.  This 
experiment  shows  that  in  the  preparation  of  nitrouracilcar- 
boxylic  acid,2  by  nitrating  4-methyluracil,  it  is  the  5-position 
that  is  first  attacked. 

Action  of  Bromine  Water:  Dibrombarbituric  Acid. — Three 
grams  of  the  above  acid  were  suspended  in  20  cc.  of  water  and 
6  grams  of  bromine  added.  Carbon  dioxide  was  given  off, 
and  the  acid  slowly  dissolved  when  more  bromine  was  added. 
The  solution  was  evaporated  in  a  flat  dish  at  about  50°.  It 
then  deposited  long,  colorless,  flat,  narrow  prisms;  one  that 
separated  was  2.5  inches  in  length. 

Calculated  for  Found. 

C4H2O3N2Br2.  I.  II.  HI. 

N  9.79  10.04         9-87  .    . 

Br  55-94  56-49 

This  material  was  compared  with  some  dibrombarbituric 
acid,  prepared  by  treating  barbituric  acid  with  bromine  and 
water,  as  above.  Similar  crystals  were  obtained.  Both 
preparations  had  the  following  properties:  they  melted, 

1  J.  Biol.  Chem.,  3,  1907. 

2  Behrend:  Ann.  Chem.  (Liebig),  229,  36  (1885). 


364  Wheeler. 

when  heated  under  the  same  conditions,  with  effervescence, 
at  235°,  and  the  melting  or  decomposing  point  was  not  altered 
when  the  two  were  mixed.  Ammonium  or  barium  hydroxide 
gave  no  color. 

When  hydrogen  sulphide  was  passed  into  the  aqueous  solu- 
tion sulphur  separated,  and  then,  on  boiling  off  the  excess 
of  hydrogen  sulphide  and  adding  barium  hydroxide,  a  purple 
or  violet-blue  precipitate  was  formed.  Baeyer1  has  shown 
that  dibrombarbituric  acid  gives  dialuric  acid  when  treated 
with  hydrogen  sulphide,  and  dialuric  acid  gives  a  violet-blue 
precipitate  with  barium  hydroxide,  as  observed  by  Behrend 
and  Roosen.2  The  samples  in  alcohol  gave  precipitates  hav- 
ing the  same  appearance  when  mixed  with  alcoholic  solutions 
of  thiourea  and  ammonium  thiocyanate. 

HN CO 

I  I 

Uracil-4-methylcarboxylate,    OC  CH  . — Six- tenths 

HN CCO2CH3 

of  a  gram  of  uracil-4-carboxylic  acid  was  suspended  in  100  cc. 
of  methyl  alcohol  and  saturated  with  hydrogen  chloride. 
After  warming  a  day  the  acid  dissolved,  and  on  cooling  a  mass 
of  colorless  needles  separated.  This  ester  formed  needles 
or  prisms  from  water  and  it  melted  to  an  oil  at  230°. 

Calculated  for 

C6H6O4N2  Found. 

N  16.47  16.45 

The  Potassium  Salt,  C5H3O4N2K.— This  normal  salt  was 
formed  when  the  acid  and  potassium  hydroxide,  in  molecular 
proportions,  were  mixed  in  aqueous  solution.  Uracil-5- 
carboxylic  acid,  under  these  conditions,  gives  an  acid  salt. 
It  separated  on  cooling  the  aqueous  solution  as  a  felt-like 
mass  of  fine,  colorless  needles.  It  showed  no  signs  of  melting 
at  355°. 

Calculated  for  Found. 

C5H3O4N2K.  I.  II. 

N  14.43  14.23  14.17 

1  Ann.  Chem.  (Liebig),  130,  133  (1864) 
z  Ibid.,  251,  244  (1889). 


Researches  on  Pyrimidines.  365 

The  Barium  Salt,  (C5H3O4N2)3Ba.— This  salt  separates  in 
the  form  of  needles  or  prisms  when  hot  aqueous  solutions  of 
the  acid  and  barium  chloride  are  mixed. 

Calculated  for  Found. 

Ci0H«O8N4Ba.  I.  II. 

N  12.51  12.12  12.20 

Oxalaceticethyl  Ester  and  Ethylpseudothiourea  Hydrobro- 
mide. — Fifty  grams  of  Kahlbaum's  oxalaceticethyl  ester,  50 
grams  of  the  ethyl  bromide  addition  product  of  thiourea,  and 
22  grams  of  sodium  hydroxide,  in  a  little  over  100  cc.  of  cold 
water,  were  mixed  and  allowed  to  stand  over  night.  The 
next  day  about  10  grams  of  crystalline  material  had  separated. 
This  was  found  to  be  difficultly  soluble  in  water  and  readily 
soluble  in  hot  alcohol.  When  crystallized  from  a  mixture 
of  equal  volumes  of  alcohol  and  water  it  formed  balls  of  color- 
less needles,  which  melted  to  a  clear  oil  at  i33°-i34°.  The 
analytical  results  and  the  behavior  of  the  substance  agreed  with 
the  view  that  this  substance  is  an  addition  product. 

Calculated  for  Pound. 

CnH2o05N2S.  I.  II.  III. 

N  9-58  9  33         9-43         9-32 

When  this  substance  was  boiled  with  hydrochloric  or  hy- 
drobromic  acid  it  gave  a  product  which  melted  at  2o6°-2O7°. 
This  was  very  soluble  in  alcohol.  From  water  it  separated 
in  the  form  of  needles  or  prisms.  It  contained  sulphur,  but 
no  nitrogen,  and  since  it  was  not  a  pyrimidine  it  was  not 
further  examined.  The  alkaline  solution  from  which  the  ad- 
dition product  had  separated  was  acidified  with  hydrochloric 
acid;  a  small  amount  of  'oil  separated  but  no  mercaptopyr- 
imidine. 

Acetylethylcyanacetate  and  Ethylpseudothiourea  Hydrobro- 
mide. — Fifteen  grams  of  acetylethylcyanacetate,  prepared  by 
Haller's  method,1  were  mixed  with  18  grams  of  the  ethyl  bro- 
mide addition  product  of  thiourea  in  18  cc.  of  water  and  then 
12  grams  of  potassium  hydroxide  in  a  little  cold  water 
added.  This  produced  a  white  precipitate,  which,  after  stand  - 

1  Ann.  Chim.  Phys.  [el,  17,  207  (1889). 


366  Wheeler. 

ing  over  night,  weighed  8.4  grams.  When  this  was  crystal- 
lized from  alcohol  it  gave  colorless,  twinned,  flat  prisms,  hav- 
ing the  form  of  the  letters  x  and  y.  They  melted  at  159°, 
with  effervescence,  and  were  found  to  be  free  from  ash.  The 
analytical  results  agreed  with  the  calculated  for  an  addition 
product  of  equal  molecules  of  the  pseudourea  and  acetylethyl- 
cyanacetate.  Acids  produced  no  precipitate  in  the  alkaline 
nitrate  from  this  material. 

Calculated  for  Found. 

C,oH1703N3S.  I.  II. 

N  16.21  16.23  15.86 

When  boiled  with  alkali,  acids  or  acetic  anhydride,  the  sub- 
stance decomposed. 

Oxalmalonic  Ethyl  Ester1  and  Ethylpseudothiourea  Hydro- 
bromide.  —  These  substances  were  mixed  with  potassium  hy- 
droxide in  molecular  proportions  in  aqueous  solution.  On 
standing  over  night,  crystals  separated;  they  were  very  solu- 
ble in  hot  water  and  somewhat  less  so  in  alcohol,  from  which 
solvent  the  material  crystallized  in  the  form  of  shining  scales, 
which  melted,  with  effervescence,  at  181°.  This  material 
gave  analytical  results  agreeing  with  the  calculated  for  an  ad- 
dition product  of  2  molecules  of  the  pseudourea  to  i  molecule 
of  oxalmalonic  ethyl  ester. 

Calculated  for  Found. 

I.  II. 


N  11.96  n-95  12.08 

When  two  molecular  proportions  of  potassium  hydroxide 
were  used,  a  granular  potassium  salt  separated  which  was 
free  from  sulphur. 

NEW  HAVEN,  CONN., 
May,  1907. 


Bouveault:  Bull.  Soc.  Chim.  [3],  19,  78  (1898). 


[Reprinted  from  the  American  Chemical  Journal,    Vol.  XXXVIII,    No.  2. 
August,  1907.] 


Contributions  from  the  Sheffield  Laboratory  of  Yale  University. 

.— RESEARCHES    ON  PYRIMIDINfiS:     THE     AC- 
TION OF  METHYL   IODIDE   ON    2-ANILINO-6- 
OXYPYRIMIDINE,     AND     THE     SYN- 
THESIS OF  2-ANILINOPYRIMI- 
DINE. 

[TWENTY-FIRST  PAPER.] 

BY  TREAT  B .  JOHNSON  AND  P.  W.  HBYL. 

The  writers  have  shown,  in  a  previous  paper,1  that  methyl 
iodide  and  ethyl  iodide  react  with  2-ethylmercapto-6-oxy- 
pyrimidine  in  presence  of  alkali,  giving  i-methyl-2-ethylmer- 
capto-6-oxypyrimidine,  I.,  and  i-ethyl-2-ethylmercapto-6- 
oxypyrimidine,  II.  The  formation  of  isomeric  oxygen  deriva- 
tives, III.,  or  3-alkyl  pyrimidines,  IV.,  was  not  observed. 


COR 


H 
III.  IV. 


It  seemed  of  interest  to  examine  the  behavior  of  methyl 
iodide    towards    2-anilino-6-oxypyrimidine,2    V.     This     pyr- 


1  THIS  JOURNAL,  37,  628. 

*  J.  Biol.  Chem.,  1,  305  (1906). 


238  Johnson  and  Hey  I. 

imidine,  theoretically,  might  give  4  isomeric  monomethyl 
derivatives,  viz., 2-anilino-6-methoxypyrimidine,  VII.,  i-methyl- 
2-anilino  -  6  -  oxypyrimidine,  VIII. ,  2  -  anilino-3-methyl  -  6  -  oxy- 
pyrimidine,  IX.,  and  2-methylanilino-6-oxypyrimidine,  X. 


NH  —  CO 

i            i 

NH—  CO 

i            i 

C6H5NH.C 

II 

CH        or 

H 

C.H8N:C          CH. 

1            11 

II 
N 

II 
CH 

NH  CH 

N 

1 
C6H6NH.C 

N 

V. 

—  •  —  PHPTT 

VI. 

PTT  1ST             PO 

V^UV^Jtlg 

CH       , 

II 
CH 

V^-doXN                          V'W 

1      1 

CeH5NH.C          CH, 

1             II 
N  CH 

VII. 

VIII. 

N- 

II 
C6H6NH.C 

CH3N- 

CO 

k 

1! 

CH 

IX. 

NH  CO 

$N>N.C          CH. 

r  PT  /      ii         ii 

^6^5 

NPTT 

V^Xl 

X. 

We  find  that  2-anilino-6-oxypyrimidine,  V.,  reacts  with 
methyl  iodide,  in  the  presence  of  potassium  hydroxide,  giving 
two  monomethyl  derivatives — 2-anilino-6-methoxypyrimidine, 
VII.,  and  i-methyl-2-anilino-6-oxypyrimidine,  VIII.  The 
structure  of  these  two  pyrimidines  was  shown  in  the  following 
manner:  The  same  methoxypyrimidine  (m.  p.  119°)  was  ob- 
tained when  2-anilino-6-chlorpyrimidine  was  warmed  with 
sodium  methylate.  A  quantitative  yield  of  the  pyrimidine 
was  also  formed  when  methyl  iodide  was  allowed  to  act  on 
the  silver  salt  of  2-anilino-6-oxypyrimidine  at  ordinary  tem- 
perature. 


Researches  on  Pyrimidines.  239 

N=C.OCH, 

C.H5NH.C          CH          -f  NaCl. 

II  II 

N CH 

The  second  isomer  was  identical  with  the  methyl  pyrimidine 
obtained  by  heating  i-methyl-2-ethylmercapto-6-oxypyrimi- 
dine,1  I.,  with  aniline  at  150°.  It  was  soluble  in  alkali  and 


C.H6SH. 


melted  at  149°-  150°.  The  isomeric  2-methylanilino-6-dKy* 
pyrimidine,  X.,  which  was  prepared  by  heating  2-ethylmer* 
capto-6-oxypyrimidine  \vith  methyl  aniline,  melted  at  187°. 

NH—  CO 

I  I 

C2H5SC  CH  +  CH8NH.C6H6    = 

N  -  CH 


C2H5SH. 


2-Amlino-6-axypyrimidine  reacts  in  a  smooth  manner  with 
phosphorus  oxyehloride  to  give  2-anilino-6-chlorpyriinidine, 
XI.  When  this  was  digested  with  water  and  zinc  dust  it  was 
reduced  practically  quantitatively  to  2-anilinopyrimidine, 
XII. 

1  Johnson  and  Heyl:  Loc.  cit. 


Johnson  and  Heyl. 

Cl  N CH 

CH     »-*>•   CeH5NH.C  CH. 


All  attempts  to  hydrolize  2-anilinopyrimidine,  XII.,  and 
2-anilino-6-oxypyrimidine  to  2-oxypyrimidine  and  uracil, 
respectively,  were  unsuccessful.  They  could  be  digested  for 
hours  with  concentrated  hydrochloric  acid  without  altera- 
tion. 2-Anilinopyrimidine  was  completely  decomposed  when 
heated  with  hydrochloric  acid  at  168°.  On  the  other  hand, 
2-anilino-6-oxypyrimidine  was  not  changed  by  this  treat- 
ment, and  was  also  recovered  unaltered  after  heating  with  20 
per  cent  sulphuric  acid  at  230°. 

The  above  pyrimidines  might  be  expected  to  react  with 
carbon  bisulphide,  giving  2-thiopyrimidine,  XIII.,  and  2-thio- 
uracil,  XIV.,  with  formation  of  phenylisocyanate.  We  find, 

N==CH  NH CO 

I  I  h*       I  I 

CS        CH  CS        CH 

I            II                                            I  II 

NH CH  NH CH 

XIII.  XIV. 

on  the  other  hand,  that  they  are  extremely  stable  in  presence 
of  this  reagent,  and  were  recovered  ualtered  after  heating 
with  carbon  bisulphide  at  230°. 

We  examined,  in  the  course  of  our  work,  the  action  of  ani- 
line and  ammonia  on  2-ethylmercapto-5-ethoxy-6-oxypyr- 
imidine,1  XV.  We  find  that  this  mercaptopyrimidine  shows 
no  tendency  to  react  with  aniline  at  100°.  In  order  to  intro- 
duce the  anilino  group  it  was  necessary  to  heat  for  several 
hours  at  200°.  This  behavior  is  of  interest  since  2-ethylmer- 
capto-6-oxypyrimidine2  and  2-ethylmercapto-5-brom-6-oxy- 
pyrimidine3  react  with  aniline  at  100°  to  give  quantitative 

1  Johnson  and  McCollum:  J.  Biol.  Chem.,  1,  437. 

*  Johnson  and  Johns:  Loc.  ctt. 

•  Wheeler  and  Bristol:  THIS  JOURNAL,  33,  437. 


Researches  on    Pyrimidines.  241 

yields  of  the  corresponding  2-anilinopyrimidines.  2-Ethyl- 
mercapto-5-ethoxy-6-oxypyrimidine  was  also  recovered  un- 
altered after  heating  with  ammonia  at  230°. 

NH CO  NH CO 

C2H5S.C          COCSH5     »->-     C6H5NH.C          COC,H5      »-*• 

N CH 

XVI. 

N=  =CH 

I  I 
COC,H5         »-»         C6H5NHC           COC2H6. 

II  II 
N CH 

XVIII. 

2-Anilino-5-ethoxy-6-oxypyrimidine,  XVI.,  reacted  with 
phosphorus  oxychloride  to  give  a  good  yield  of  2-anilino-5- 
ethoxy-6-chlorpyrimidine,  XVII.  When  this  chloride  was 
heated  with  ammonia  a  quantitative  yield  of  2-anilino-5- 
ethoxy-6-aminopyrimidine  was  obtained.  2-Anilino-5-ethoxy- 
pyrimidine,  XVIII.,  was  prepared  by  reducing  the  chlorpyr- 
imidine,  XVII.,  with  zinc  dust. 

EXPERIMENTAL. 

N=  =C.OCHS 

I  I 

2-Anilino-6-methoxypyrimidine,    C6H5HN.C          CH         . — 

N CH 

This  pyrimidine  was  obtained  when  methyl  iodide  was  allowed 
to  act  on  the  silver  salt  of  2-anilino-6-oxypyrimidine1  at  ordi- 
nary temperature.  It  was  also  prepared  by  treating  2-ariilino- 
6-chlorpyrimidine  with  sodium  me  thy  late.  It  deposited  from 
95  per  cent  alcohol  in  transparent  prisms  that  melted  at  119°  to 
a  clear  oil.  It  was  converted  into  2-anilino-6-oxypyrimidine 
(m.  p.  231°)  when  digested  with  20  per  cent  hydrochloric 
acid.  Analysis  (Kjeldahl): 

1  Johnson  and  Johns:  Loc.  cit. 


242  .        Johnson  and  Heyl. 

Calculated  for 


Found. 

N  20.89  20.93 

i-Methyl-2-anilino-6-oxypyrimidine, 
CH.N  -  CO 

I  I   , 

CBH5HN  .C  CH  .H,O  —  Molecular  proportions  of  2  -anilino- 

II  II 
N  -  CH 

6-oxypyrimidine  (20  grams)  and  potassium  hydroxide  (6 
grams)  were  dissolved  in  95  per  cent  alcohol.  Twenty  grams 
of  methyl  iodide  were  then  added  and  the  solution  heated  on 
the  steam-bath  until  it  failed  to  give  an  alkaline  reaction 
with  turmeric.  The  solution  was  then  filtered  from  insoluble 
potassium  iodide  and  the  excess  of  alcohol  evaporated  on  the 
steam-bath.  We  obtained  a  syrup  which  deposited  a  crys- 
talline precipitate  when  treated  with  cold  water.  This  was 
separated  and  triturated  with  a  10  per  cent  sodium  hydroxide 
solution  and  the  insoluble  portion  purified  by  crystallization 
from  95  per  cent  alcohol.  It  separated  in  prismatic  crystals 
that  melted  at  1  19  °  to  a  clear  oil.  It  was  identified  as  2-anilino- 
6-methoxypyrimidine.  A  mixture  of  the  2  compounds  melted 
sharp  at  119°.  Analysis  (Kjeldahl): 

Calculated  for 
CnHiiON8.  Found. 

N  20.89  21.2 

When  the  sodium  hydroxide  filtrate  (above)  was  acidified 
with  acetic  acid  a  mixture  of  2-anilino-6-oxypyrimidine  and 
i-methyl-2-anilino-6-oxypyrimidine  separated.  After  a  frac- 
tional crystallization  from  alcohol  and  repeated  recrystalli- 
zations  from  benzene  and  water  the  methylpyrimidine  was 
obtained  pure.  It  deposited  from  hot  water  in  slender  prisms, 
that  melted  at  i49°-i5o°  to  a  clear  oil.  It  contained  i  mole- 
cule of  water  of  crystallization,  which  was  determined  by 
heating  at  ioo°-no°. 

0.8187  gram  substance  lost  0.0686  gram. 

Calculated  for 
CiiHnON8.H2O.  Found. 

H2O  8.21  8.37 


Researches  on  Pyrimidines.  243 

Analysis  of  anhydrous  material : 

0.2333  gram  substance  gave  0.5597  gram  CO2  and  0.1130 
gram  H2O. 

Nitrogen  determined  by  Kjeldahl  method : 

Calculated  for 
CiiHnON3.  Found. 

C  65.43  65.67 

H  5.38  5-47 

N  20.89  20.55 

Action  of  Aniline  on  i-Methyl-2-ethylmercapto-6-oxypyr- 
imidine.1 — The  mercaptopyrimidine  was  recovered  unaltered 
after  heating  with  aniline  for  several  hours  at  100°.  One 
and  two-tenths  grams  of  the  mercaptopyrimidine  and  0.7 
gram  of  aniline  were  heated  for  7  hours  at  i25°-i55°.  The 
excess  of  aniline  was  then  removed  by  distillation  with  steam 
and  the  insoluble  residue  treated  with  hot  benzene.  A  crys- 
talline compound  separated  from  the  benzene  on  cooling. 
It  was  purified  by  recrystallization  from  water  and  deposited 
in  prisms  that  melted  at  i49°-i5O°.  When  this  derivative 
was  mixed  with  some  i-methyl-2-anilino-6-oxypyrimidine  (m. 
p.  i49°-i5o°),  the  melting  point  was  not  changed.  Analysis 
(Kjeldahl): 

Calculated  for 
CiiHuONs.  Found. 

N  20 . 89  2O  .  6 

NH CO 

&• 


2  -  Methylanilino  -  6-  oxypyrimidine,  ^>N  .C 

N CH 

This  pyrimidine  was  prepared  by  heating  7  grams  of  2-ethylmer- 
capto-6-oxypyrimidine2  with  6  grains  of  methyl  aniline  for 
14  hours  at  100°.  It  was  soluble  in  warm  benzene  and  alcohol. 
It  separated  from  hot  alcohol  in  large,  prismatic  crystals  that 
melted  at  187°  to  a  clear  oil.  The  yield  corresponded  to  about 
74  per  cent  of  the  theoretical.  Analysis  (Kjeldahl) : 

1  Johnson  and  Heyl:    Loc.  tit. 

*  Wheeler  and  Merriam:   THIS  JOURNAL,  29,  478  (1903). 


244  Johnson  and  Heyl. 

Calculated  for  Found. 

CuHuON8.  I.  II. 

N  20.89  20.55  20.66 

N CC1. 

2-Anilino-6-chlorpyrimidine,  C6H5NH.C  CH. — The  hy- 

N CH 

drochloride  of  this  pyrimidine  was  obtained  when  2-anilino-6- 
oxypyrimidine  was  warmed  with  an  excess  of  phosphorus 
oxychloride.  After  the  evolution  of  hydrochloric  acid  had 
ceased  the  solution  was  poured  upon  crushed  ice  to  destroy 
the  excess  of  phosphorus  oxychloride.  The  hydrochloride 
of  2-anilino-6-chlorpyrimidine  separated  as  a  thick  varnish, 
which  soon  solidified.  This  salt  was  triturated  with  a  dilute 
solution  of  sodium  hydroxide  or  ammonia  when  the  chlorpyr- 
imidine  deposited.  It  crystallized  from  alcohol  in  plates 
that  melted  at  134°  to  an  oil.  Analysis  (Kjeldahl): 

Calculated  for  Found. 

CioH8N3Cl.  I.  II. 

N  20.43  20.09  20.3 

Nz=  =:CH 

I  I 

2-Anilinopyrimidine,    C6H5NH.C  CH. — Five  and   five- 

N CH 

tenths  grams  of  2-anilino-6-chlorpyrimidine  and  30  grams  of 
zinc  dust  were  suspended  in  400  cc.  of  water  and  the  mixture 
boiled  for  2.5  hours.  The  solution  was  then  filtered  and  the 
residue  of  zinc  dust  extracted  twice  with  300  cc.  of  boiling 
water.  The  aqueous  filtrates  were  combined  and  concentra- 
ted to  one-half  their  volume,  when  the  anilinopyrimidine 
separated,  on  cooling,  in  characteristic,  slender  prisms.  The 
yield  was  3.3  grams,  or  78  per  cent  of  the  theoretical.  The 
base  was  practically  insoluble  in  cold  and  difficultly  soluble 
in  hot  water.  It  crystallized  from  95  per  cent  alcohol  in  pris- 
matic crystals  that  melted  at  116°  to  a  clear  oil.  Analysis 
(Kjeldahl) : 


Researches  on  Pyrimidines.  245 

Calculated  for 

C10H9N3.  Found. 

N  24.56  24.22 

2-Anilinopyrimidine  could  be  boiled  with  concentrated  hy- 
drochloric acid  without  change.  One  gram  of  the  base  was 
heated  with  about  5  cc.  of  concentrated  hydrochloric  acid 
for  2  hours  at  i48°-i68°.  Under  these  conditions  it  was  de- 
composed into  tarry  products,  from  which  nothing  definite 
was  isolated.  An  attempt  was  made  to  convert  i-anilino- 
pyrimidine  into  2-thiopyrimidine  by  heating  with  carbon  bi- 
sulphide. One  gram  of  the  pyrimidine  was  heated  with  6  cc. 
of  carbon  bisulphide,  for  4  hours  at  I9o°-i95°.  We  obtained  a 
clear  solution  which  deposited  beautiful,  needle-like  prisms  that 
melted  at  116°.  The  compound  gave  no  test  for  sulphur 
and  was  identified  as  unaltered  material. 

The  Hydrochloric  Acid  Salt. — This  salt  was  extremely  solu- 
ble in  water  and  alcohol.  It  had  no  definite  melting  point, 
but  decomposed  when  heated  above  125°.  Analysis  (Kjel- 
dahl) : 

Calculated  for 

Ci0H9N8.HCl.  Found. 

N  20.24  19-77 

The  Sulphuric  Acid  Salt. — This  salt  separated  from  20  per 
cent  sulphuric  acid  in  elongated  prisms  that  melted  at  140°- 
142°.  The  salt  dissociates  when  warmed  in  aqueous  solu- 
tions. Analysis : 

Calculated  for 
CioH9N3.H2SO4.        (Ci0H9N3)2H2SO4.  Found. 

N  15.5  19.09  15.10 

The  Platinum  Chloride  Double  Salt. — This  salt  separated  in 
yellow  rosettes  when  a  hydrochloric  acid  solution  of  the  base 
was  treated  with  hydrogen -platinic  chloride.  The  salt  was 
slowly  decomposed  in  boiling  water  and  metallic  platinum 
deposited.  It  melted  with  decomposition  at  2i8°-22i°. 

Calculated  for 
(C10H9N3.HCl)2.PtCl4.  Found. 

Pt  25.91  26.6 


246  Johnson  and  Heyl. 

Behavior  of  2-Anilino-6-oxypyrimidine  towards  Hydro- 
chloric and  Sulphuric  Acids. — This  pyrimidine  is  more  stable  in 
presence  of  acids  than  2-anilinopyrimidine.  It  was  recovered 
unaltered  after  heating  with  concentrated  hydrochloric  acid 
for  4  hours  at  i5O°-i6o°.  It  was  not  decomposed  after  heat- 
ing with  25  per  cent  sulphuric  acid  at  230°  for  2  hours. 

Behavior  of  2-Anilino-6-oxypyrimidine  toivards  Carbon  Bi- 
sulphide.— There  were  no  indications  of  any  reaction  after 
heating  2  grams  of  the  pyrimidine  with  5  cc.  of  carbon  bisul- 
phide for  5  hours,  at  150°- 1 60°.  The  mixture  was  then  heated 
for  3  hours  at  1 85  °-2 15°.  When  the  tube  was  opened  there  was 
no  pressure  and  the  ualtered  pyrimidine  was  recovered  melt- 
ing at  229°.  In  a  third  experiment  i  gram  of  the  pyrimidine 
was  heated  with  5  cc.  of  carbon  bisulphide  for  6  hours,  at 
230°.  When  the  tube  was  opened  there  was  some  pressure 
due  to  the  presence  of  hydrogen  sulphide  and  a  crystalline 
residue  was  suspended  in  the  carbon  bisulphide.  This  was 
identified  as  the  unaltered  pyrimidine;  it  melted  at  228°- 
229°,  and  when  mixed  with  2-anilino-6-oxypyrimidine  the 
melting  point  was  not  changed.  Analysis  (Kjeldahl) : 

Calculated  for 
C10H9ON3.  Found. 

N  22.46  22.17 

t 

Hydrochloride  of  2-Ethylmercapto- 5 ,6 -diethoxy pyrimidine, 
N=  =COC3H5 

C7H5SC  COC2H5.HC1.— This  pyrimidine  was  obtained  as 

II  II 

N CH 

an  oil  by  treatment  of  2-ethylmercapto-5-ethoxy-6-chlorpyr- 
imidine1  with  the  calculated  quantity  of  sodium  ethylate. 
When  an  ether  solution  of  the  pyrimidine  was  saturated  with 
dry  hydrochloric  acid  gas  the  salt  deposited  in  prismatic 
crystals  that  melted  with  decomposition  at  i29°-i3i°.  The 
salt  was  hydroscopic.  Analysis  (Kjeldahl) : 

Calculated  for 
CioH6O2N2S.HCl.  Found. 

N  10.58  10.55 

1  Johnson  and  McCollum:  J.  Biol.  Chem.,  1,  443  (1906). 


Researches  on  Pyrimidines.  247 

Action  of  Ammonia  on  2-Methylmercapto-^-ethoxy-6-oxy- 
pyrimidine.  —  This  mercapto  pyrimidine  was  recovered  unal- 
tered after  heating  with  concentrated  alcoholic  ammonia  for 
2  hours  at  I4o°-i6o°  and  again  for  1.5  hours  at  2io°-235°. 

2-  A  nilino-5-eihoxy-6-oxy  pyrimidine, 
NH  -  CO 

I  I 

C6H5H  N.C  C.OC2H5.—  2-Ethylmercapto-5-ethoxy-6-oxy- 

N  ---  CH 

pyrimidine1  was  recovered  unaltered  after  heating  with  ani- 
line on  the  steam-bath  for  several  hours.  Four  grams  of  the 
mercaptopyrimidine  and  2  grams  of  .aniline  were  dissolved  in 
10  cc.  of  alcohol  and  heated  for  2  hours  at  i85°-2i6°.  When 
the  tube  was  examined  the  presence  of  ethyl  rnercaptan  was 
apparent,  and  a  crystalline  residue  had  deposited.  This  was 
a  mixture  of  unaltered  mercaptopyrimidine  and  the  anilino 
derivative  that  melted  above  160°.  The  anilino  compound 
was  separated  from  the  mercapto  derivative  by  dissolving  in 
cold  dilute  hydrochloric  acid  and  making  alkaline  with  am- 
monia. The  anilino  derivative  deposited  in  plates  and  was 
purified  for  analysis  by  recrystallization  from  alcohol.  It 
melted  at  23i°-232°.  In  a  second  experiment  we  heated  10 
grams  of  the  mercaptopyrimidine  and  5.1  grams  of  aniline 
for  6  hours  at  i9o°-2Oo°  and  obtained  6.8  grams  of  crude 
anilino  compound  melting  at  2i4°-22o°.  We  did  not  observe 
the  formation  of  any  2,5-dianilino-6-oxypyrimidine  under 
the  conditions  employed.  Analysis  (Kjeldahl)  : 

Calculated  for 
Ci2Hi3O2N3.  Found. 

N  18.18  18.10 

2-Anilino-_5-ethoxy-6-chlorpyrimidine, 


C6H5HNC  COC2H5  —  Ten  and  five-tenths  grams  of  2-ani- 

II  II 

N  --  CH 

lino-5-ethoxy-6-oxypyrimidine   were   warmed   with   30   cc.    of 

1  Johnson  and  McCollum:  Loc.  cit. 


248  Johnson  and  Heyl. 

phosphorus  oxychloride  until  the  evolution  of  hydrochloric 
acid  ceased.  The  solution  was  then  poured  upon  crushed 
ice,  when  the  chlorpyrimidine  separated  as  a  semi-solid.  The 
chloride  was  dissolved  in  ether  and  thoroughly  dried  with 
calcium  chloride.  When  the  ether  was  evaporated  the  chlor- 
ide deposited  in  prismatic  crystals  that  were  extremely  solu- 
ble in  organic  solvents.  The  compound  crystallized  from 
alcohol  in  stout  prisms,  that  melted  at  ni°-ii20  to  an  oil. 
Analysis  (Kjeldahl) : 

Calculated  for 

Ci2H12ON3Cl.  Found. 

N  16.82  16.55 

N=  =CH 
.    I  I 

2- Anilino-5-eihoxy pyrimidine,  C8H5NHC          COO2H5. — One 

N CH 

gram  of  2-anilino-5-ethoxy-6-chlorpyrimidine  was  digested 
for  i  hour  with  to  grams  of  zinc  dust  and  150  cc.  of  water. 
When  the  hot  mixture  was  filtered  the  pyrimidine  deposited 
in  prismatic  crystals.  It  was  difficultly  soluble  in  water 
and  more  was  obtained  by  repeatedly  extracting  the  zinc  resi- 
due with  hot  water.  The  pyrimidine  dissolves  in  concentra- 
ted sulphuric  acid  to  give  a  yellow  solution.  It  crystallized 
from  95  per  cent  alcohol  in  short  prisms  that  melted  to  a  clear 
oil  at  I30°-i3i°.  Analysis  (Kjeldahl): 

Calculated  for  Found. 

C12H18ON8.  I.  II. 

N  19.53  18.98  19.33 

2-Anilino-5-etho%y-6-aminopyrimidine, 
N=C.NH2 

C6H5NH.C          COC2H5 — This  pyrimidine  was  obtained  when 

II  II 

N CH 

2-anilino-5-ethoxy-6-chlorpyrimidine  was  heated  with  alco- 
holic ammonia  at  i8o°-i88°.  When  i  gram  of  the  chloride 
was  heated  with  alcoholic  ammonia,  for  2  hours,  at  150°, 


Researches  on  Pyrimidines.  249 

the  reaction  was  not  complete,  and  the  product  obtained  gave 
a  pronounced  test  for  chlorine  after  crystallization  from  alco- 
hol. The  pyrimidine  crystallized  from  95  per  cent  alcohol 
in  prisms  that  melted  at  133°— 134°  to  a  clear  oil.  Analysis 
(Kjeldahl): 

Calculated  for 
CiaH14ON4.  Found. 

N  24.34  24.06 

NBW  HAVEN,  CONN., 
June  15.  1907. 


vnoi  'i>  -to!  Jrf^J  bsO 

[ju-tevio    onibin.hvq    yrIT      -loii 


,.'//ioD  .HJIVA 
.70Q1    ?-I 


VI.— RESEARCHES  ON  PYRIMIDINS:  SYNTHESIS  OF 
THYMIN-4-CARBOXYLIC  ACID. 

BY  TREAT  B.  JOHNSON. 

(From  the  Sheffield  Laboratory  of  Yale  University.) 
(Received  for  publication,  June  27,  1907.) 

I  shall  describe,  in  this  paper,  the  preparation  and  properties 
of  thymin-4-carboxylic  acid, 

NH— CO 

I          I 
CO      CCH3 

I          II 
NH — CCOOH 

The  study  of  the  carboxylic  acids  of  uracil,  cytosin  and  thymin 
is  of  interest  on  account  of  the  possibility  that  these  pyrimidins 
may  be  linked  in  nucleic  acids  by  acid  amide  groupings,  — CO.NH. 
It  has  already  been  shown1  that  uracil  may  exist  in  nucleic  acids 
as  a  5-carboxyl  compound  since  uracil- 5 -carboxylic  acid  can  be 
quantitatively  converted  into  uracil  if  heated  with  20  per  cent 
sulphuric  acid  at  160-170°.  I  now  find  that  thymin-4-carbox- 
ylic  acid  can  be  heated  with  20  per  cent  sulphuric  acid,  under 
the  same  conditions,  without  alteration.  Thymin  therefore  can- 
not exist  in  the  nucleic  acids  as  a  ^.-carboxyl  compound. 

Wislicenus  observed  that  diethyl  oxalacetate  and  its  homo- 
logues  show  a  wide  difference  in  their  behavior  towards  ammonia 
and  amines.  Diethyl  oxalacetate,  for  example,  combines  with 
ammonia  to  form  an  unstable  addition  product,  which  is  changed 
to  an  ammonium  salt  of  the  lactone  ester  of  oxalcitric  acid  (I)2 
when  warmed  with  alcohol. 

Diethyl  methyloxalacetate,  on  the  other  hand,  does  not  form 

1  Amer.  Chem.  Journ.,  xxxvii,  p.  392. 

2  Wislicenus  and  Beckh:  Ber.  d.  deutsch.  chem.  Gesellsch.,  xxviii,  p.  789; 
Ann.  d.  Chem.  (Liebig),  ccxcv,  p.  339. 

299 


300  Researches  on  Pyrimidins 

an  addition  product  with  ammonia  but  reacts  at  110°,  giving 
aminomethylmaleinimide  (II).1 


C2H602C-CH 

C02C2H6 

II 

Another  striking  example  of  this  difference  between  diethyl 
oxalacetate  and  diethyl  methyloxalacetate  was  found  when  we 
investigated  the  behavior  of  pseudothioureas  towards  these  esters. 
Pseudoethylthiourea  combines  with  diethyl  oxalacetate,  giving 
a  stable  addition  product  (Professor  Wheeler) . 

On  the  other  hand,  diethyl  methyloxalacetate  reacts  with 
pseudomethylthiourea,  in  presence  of  potassium  hydroxide,  giv- 
ing a  good  yield  of  the  potassium  salt  of  2-methylmercapto-4- 
carboxyl-5-methyl-6-oxypyrimidin  (III).  The  condensation  can 
be  represented  as  follows: 

NH,  COOC2H5  NH— CO 

I  !  II 

C2H5SC       +        C-CH3  CH3SC         C'CH3+ 2C2H5OH. 

II  II  II      il 

NH      HO-C'COOC2H5  N — C'COOH 

III 

2-Methylmercapto-4-carbethoxy  -  5  -  methyl  -  6-oxypyrimidin  (V) 
was  obtained,  in  one  experiment,  as  a  secondary  product  of  the 
condensation. 

2-Methylmercapto-4  -  carboxyl-5-methyl-6-oxypyrimidin  (III) 
can  be  converted  into  thymin-4-carboxylic  acid  (VII),  by  digest- 
ing with  concentrated  hydrochloric  acid.  When  this  acid  was 
boiled,  in  ethyl  alcohol  solution,  with  a  small  quantity  of  sul- 
phuric acid  it  was  converted  into  thymin-4-ethylcarboxylate 
(VIII).  This  same  ester  was  also  obtained  when  2-methylmer- 
capto-4-carbethoxy-5-methyl-6-oxypyrimidin  (V),  was  boiled  in 
alcoholic  solution  with  sulphuric  acid.  When  thymin-4-car- 
boxylic  acid  (VII),  is  melted  it  undergoes  complete  decom- 

1  Wislicenus  and  Kiesewetter:  Ber.  d.  deutsch.  chem.  Gesellsch.,  xxxi, 
p.  194. 


Treat  B.  Johnson  301 

position.  On  the  other  hand,  2-methylmercapto-4-carboxyl-5- 
methyl-6-oxypyrimidin  (III),  melts  with  evolution  of  carbon- 
dioxide  and  is  converted  quantitatively  into  2-methylmercapto- 
5-methyl-6-oxypyrimidin  (IV).  This  mercaptopyrimidin  can 
then  be  changed  to  thymin  (VI)  by  boiling  with  hydrochloric 
acid.1 

The  formation  of  thymin  in  this  manner  from  2-methylmer- 
capto-4-carboxyl-5-methyl-6-oxypyrimidin  (III),  shows  that  the 
condensation  takes  place  as  represented  in  the  preceding  equa- 
tion and  that  the  product  is  not  a  hydantoin  derivative.  The 
above  compounds  and  their  various  transformations  are  repre- 
sented as  follows: 

NH — CO  NH — CO  NH — CO 

II  II  II 

CH3SC         CCH3  < 

II          II 
N  —  CH 

r 

NH— CO 

I  I 

CO      CCH, 

I  II 

NH— CH 

VI 

Thymin-4-carboxylic  acid  is  characterized  by  its  insolubility 
in  cold  water  and  by  its  property  of  crystallizing  from  aqueous 
solution  with  and  without  water  of  crystallization.  It  gives  very 
insoluble  barium  and  lead  salts,  and  is  not  precipitated  by  phos- 
photungstic  acid. 

Thymin-4-carboxylic  acid  reacts  in  the  normal  manner  with 
bromine  water  giving  oxybromhydrothymin-4-carboxylic  acid 
(IX). 

NH— CO  NH — CO 

II  I  I       CH 

CO       C-CH,,  +  Br,  +  H2O        =       CO       C  <  ~"3    +    HBr 

II  I  I 

NH — CCOOH  NH— C'OH 

COOH 
IX 

1  Amer.  Chem.  Journ.,  xxix,  p.  487. 


3C         CCH       +± 

II           II 

CH3SC         CCH3 

II          II 

II           II 
N  —  CCOOH 

I1" 

NH—  CO 

1            1 

II          II 
N  —  CCO2C2H, 

r 

NH—  CO 

1           1 

1            1 
CO       CCH3         <=> 

\          II 
NH—  CCOOH 

VII 

1           1 
CO       C-CH3 

1           II 
NH—  CCO2C2HS 
VIII 

302  Researches  on  Pyrimidins 


EXPERIMENTAL. 

2-Methylmercapto-4.-carboxyl-5-methyl-6-oxypyrimidin, 

NH  —  CO 

I  I 
CH3S-C          C-CH3 

II  II 

N  —  C-COOH 

Thirty  grams  of  pseudornethylthiourea  hydriodide  and  50  grams 
of  the  sodium  salt  of  diethyl  oxalpropionate  were  dissolved  in 
about  500  cc.  of  water  and  two  molecular  proportions  of  potassium 
hydroxide  (16  grams)  added  to  the  solution.  The  mixture  was 
allowed  to  stand  on  the  steam-oven  for  8-10  hours  and  then 
concentrated  to  a  volume  of  150  cc.  After  thorough  cooling, 
and  acidifying  with  hydrochloric  acid,  the  mercapto-pyrimidin 
deposited  in  prismatic  crystals.  It  was  practically  insoluble  in 
cold  water  and  difficultly  soluble  in  boiling  water  and  alcohol. 
It  separated  from  water  or  alcohol  in  rectangular  prisms  that 
melted  at  243-244°  with  effervescence  to  a  clear  oil.  It  deposited 
from  glacial  acetic  acid  in  stout  prismatic  crystals.  The  yield 
of  acid  corresponded  to  about  80  per  cent  of  the  theoretical. 
Analysis  (Kjeldahl)  : 

Calculated  for 
C7H8O3N2S:  Found: 

N  ...................  14.  00  per  cent.  13.88  per  cent. 

2-Methylmercapto-4.-carbethoxy-5-methyl-6-oxypyrimidin, 

NH—  CO 

I  I 
CH3SC         CCH3 

II  II 

N  —  CCOOC2H5 

This  ester  was  obtained,  associated  with  2-methylmercapto- 
4-carboxyl-5-methyl-6-oxypyrimidin,  when  I  used  one  instead 
of  two  molecular  proportions  of  potassium  hydroxide  in  the 
above  condensation.  It  was  difficultly  soluble  in  cold  water  and 
alcohol,  but  deposited  from  hot  alcohol  or  water  in  slender  needles 
that  melted  at  201—202°  to  a  clear  oil  without  effervescence.  An- 
alysis (Kjeldahl): 

Calculated  for 

Found: 


N  ...................  12.  30  per  cent.  12.37  per  cent. 


Treat  B.  Johnson  303 

Potassium  Salt  of  2-Methylmercapto-^-carboxyl-^-methyl-6-oxy- 
pyrimidin, 

NH— CO 

I  I 

CH3SC         C-CH3'6H2O 

'    II  II 

N  —  CCOOK 

A  good  yield  of  this  salt  was  obtained  under  the  following  con- 
ditions: Pseudomethylthiourea  and  diethyl  oxalpropionate  were 
condensed  as  in  the  above  experiment,  in  presence  of  two  mole- 
cular proportions  of  potassium  hydroxide.  After  standing  for 
about  twelve  hours  at  40-45°  the  solution  was  then  acidified  with 
acetic  acid  and  concentrated  to  a  volume  of  about  150  cc.  On 
cooling  the  potassium  salt  deposited  in  distorted  needles  that 
decomposed  with  effervescence  when  heated  above  230°.  When 
this  acetic  acid  filtrate  was  treated  with  hydrochloric  acid  the 
mercapto-acid  separated  melting  at  243°.  The  potassium  salt 
was  very  soluble  in  hot  water  and  deposited,  on  cooling,  in 
needles.  They  contained  water  of  crystallization  which  was 
determined  by  heating  at  100-110°  for  two  hours. 

1.2424  gram  substance  lost  o .  4032  gram  water. 

Calculated  for  „ 

C7H7O3N2SK.6H2O: 

H2O 31.21  per  cent.  32 . 4  per  cent. 

Nitrogen  determination  in  the  anhydrous  salt  (Kjeldahl) :  4 

Calculated  for  „ 

C7H703N2SK:  Found: 

N 1 1 . 76  per  cent.  11.91  per  cent. 


Behavior  of  2-Metkylmercapto-^.-carboxyl-^-methyl-6-oxypyrimi- 
din  on  Heating. — About  two  grams  of  the  mercapto-acid  were 
heated  in  a  sulphuric  acid  bath  at  245°  until  all  effervescence 
ceased.  I  obtained  a  clear  oil  that  crystallized,  on  cooling,  in 
large,  prismatic  crystals.  When  these  prisms  were  heated  they 
melted  sharply  at  230-231°  without  effervescence  to  a  clear  oil. 
The  compound  deposited  from  water  in  flat  prisms  that  melted 
at  233°  and  was  identified  as  2-methylmercapto-5-methyl-6-oxy- 


304  Researches  on  Pyrimidins 

pyrimidin.1     When  mixed  with  this  pyrimidin  the  melting  point 
was  not  lowered.     Analysis  (Kjeldahl) : 

Calculated  for  _, 

C6H8ON2S:  Found: 

N 17.94  percent.  17.80  per  cent. 

Thymin- ^.-carboocylic  Acid, 

NH— CO 

I          I 
CO      CCH3-H20 

I          II 
NH— CCOOH 

A  quantitative  yield  of  this  acid  was  obtained  when  2-methyl- 
mercapto-4-carboxyl-5-methyl-6-oxypyrimidin  was  digested  with 
concentrated  hydrochloric  acid.  The  oxygen  acid  separated 
from  the  acid  solution  as  a  granular  powder  that  was  difficultly 
soluble  in  boiling  water  and  practically  insoluble  in  alcohol.  A 
most  characteristic  behavior  of  this  acid  is  its  property  of  crystal- 
lizing from  hot  water  in  anhydrous  condition  and  with  one  mole- 
cule of  water  of  crystallization.  When  a  hot,  saturated  aqueous 
solution  of  the  acid  was  allowed  to  cool  slowly  the  anhydrous 
acid  first  deposited  in  balls  of  microscopic  prisms  resembling 
very  much  the  crystalline  form  of  uracil.  They  decomposed 
at  328-330°  (Anschutz  thermometer)  and  did  not  lose  weight 
when  heated  at  120°.  Analysis  (Kjeldahl): 

Calculated  for 
C6H6O4N2:  Found: 

N 16 . 47  per  cent.  16 . 37  per  cent. 

After  filtering  from  the  anhydrous  acid  and  allowing  the  fil- 
trate to  stand,  transparent,  rectangular  prisms  of  the  hydrous 
acid  deposited.  They  decomposed  at  the  same  temperature 
as  the  anhydrous  acid  (3  2  8-3  3  o°) .  The  acid  was  not  precipitated 
by  phosphotungstic  acid. 

Water  determination:  0.6742  gram  substance  lost  0.0687  gram  water 
after  heating  one  hour  at  1 10-120°. 

Calculated  for 
C6H604N2.H20:  Found: 

H2O 9 . 60  per  cent.  10.1  per  cent. 

lAmer.  Chem.  Journ.,  xix,  p.  478. 


Treat  B.  Johnson  305 

Analysis  of  the  anhydrous  acid:     0.2592  gram  substance  gave  0.4002 
gram  CO2  and  o.  0854  gram  H2O.     Nitrogen  determination  (Kjeldahl) : 


C 

H 

N.. 


Calculated  for 
C6H604N2: 

42  .  35  per  cent. 
3  .  52    "     " 
16.47    "     " 

Found  : 

42.11  per  cent. 
3.66    "     " 
16.23    "     " 

Action  of  20  per  cent  Sulphuric  Acid. — One-half  a  gram  of  the 
thymin  acid  was  heated  with  5  cc.  of  20  per  cent  sulphuric  acid 
for  two  hours  at  160-170°.  When  the  tube  was  opened  there 
was  no  pressure  and  the  unaltered  acid  was  suspended  in  the 
sulphuric  acid.  I  recovered  0.45  gram  of  acid  melting  at  326- 
329°.  Analysis  (Kjeldahl): 

Calculated  for  ,-,         , 

C«H604N2:  Found: 

N 16. 47  per  cent.  16. 15  per  cent. 

Potassium  Salt,  C6H5O4N2K.2H2O.— This  salt  was  prepared 
by  dissolving  molecular  proportions  of  potassium  hydroxide  and 
thymin-4-carboxylic  acid  in  water.  When  the  solution  was 
concentrated  and  allowed  to  stand  for  a  few  hours  the  salt 
deposited  in  radiating  prisms.  It  was  dried  for  analysis  in  a 
desiccator  over  sulphuric  acid  (Kjeldahl) : 

Calculated  for  Calculated  for  „ 

C6H5O4N2K:  C6H.,O4N2K.2H2O:  Found: 

N 13 . 45  per  cent.       1 1 . 06  per  cent.  10.97  per  cent. 

Lead  Salt  (C6H5O4N2)2  Pb.— This  salt  deposited  in  well  devel- 
oped prisms  when  a  solution  of  lead  acetate  was  added  to  a  hot, 
saturated,  aqueous  solution  of  thymin-4-carboxylic  acid.  It  was 
practically  insoluble  in  cold  water.  Analysis  (Kjeldahl) : 

Calculated  for  „         , 

(C6H5O4N2)2Pb:  Found: 

N 10 . 27  per  cent.  10 . 00  per  cent. 

Barium  Salt  (C6H5O4N2)2Ba. — Thymin-4-carboxylic  acid  gives 
no  precipitate  when  treated  with  a  solution  of  barium  chloride. 
The  barium  salt  was  prepared  by  dissolving  the  acid  in  potas- 
sium hydroxide  and  then  adding  the  calculated  amount  of  barium 
chloride.  It  separated  from  water  in  corpuscular  crystals. 
Analysis  (Kjeldahl): 

Calculated  for 
(C6H6O4N212Ba:  Found: 

N 11.77  per  cent.  11 .30  per  cent. 


306  Researches  on  Pyrimidins 

Thymin-f-ethylcarboxylate, 

NH  —  CO 

I          I 
CO      CCH3 

I  II 

NH—  CCOOC2H5 

was  prepared  by  esterifying  the  acid  with  ethyl  alcohol  and 
sulphuric  acid.  It  was  also  obtained  when  2-methylmercapto- 
4-carbethoxy-5-methyl-6-oxypyrimidin  was  boiled  in  alcoholic 
solution  with  a  small  amount  of  hydrochloric  acid.  The  ester 
deposited  from  hot  water  in  distorted  prisms  that  melted  at 
255°  to  a  clear  oil  without  effervescence.  Analysis  (Kjeldahl)  : 

Calculated  for 
C8H1004N2:  Found: 

N  ...................          14.  14  per  cent.  14.07  per  cent. 

Oxybromhydrothymin-4.-carboxylic  A  cid, 

NH  —  CO 

I  I        CH 

CO      C  <utl* 

I     I   Br 

NH—  C'OH 
COOH 

Three  and  five-tenths  grams  of  finely  pulverized  thymin-4- 
carboxylic  acid  were  suspended  in  about  40  cc.  of  bromine  water 
and  bromine  slowly  added  until  the  acid  had  completely 
dissolved.  There  was  no  evolution  of  carbon  dioxide  and  when 
the  solution  was  allowed  to  evaporate  spontaneously  in  the 
atmosphere  well-developed,  prismatic  crystals  of  the  hydro- 
derivative  separated.  It  was  purified  for  analysis  by  recrys- 
tallization  from  bromine  water.  It  crystallized  in  small,  pris- 
matic crystals  that  charred  when  heated  above  270°  and  then 
decomposed  with  violent  effervescence  from  295-300°  accord- 
ing to  the  rate  of  heating.  When  thymin-4-carboxylic  acid  was 
heated  with  bromine  water  at  146-152°  it  was  completely  decom- 
posed with  formation  of  bromoform.  Analysis  (Kjeldahl)  : 

Calculated  for  Calculated  for  Found: 

C5H5O3N2Br:  I.  II. 


N  .....   10.  48  per  cent.   12.66  per  cent.   10.45  10.45  per  cent. 


[Reprinted  from  the  American  Chemical  Journal,   Vol.  XXXVIII. 
No.  5.    November,  1907.] 


Contributions  from  the  Sheffield  Laboratory  of  Yale  University. 

CXLIX.  — RESEARCHES    ON    PYRIMIDINES:    SYN- 
THESIS   OF    CYTOSINE-5-CARBOXYLIC    ACID. 

(TWENTY-SIXTH  PAPER.) 

BY  HENRY  I,.  WHEKLER  AND  CARL  O.  JOHNS. 

The  present  work  was  undertaken  with  the  obj'ect  of  making 
a  study  of  some  material  to  be  used  for  further  syntheses,  and 
also  in  order  to  examine  the  properties  of  cytosine-5-carboxylic 
acid  and  some  of  its  derivatives.  The  acid  has  now  been  pre- 
pared by  means  of  the  following  reactions:  In  a  previous 
paper1  we  showed  that  ethoxymethylenmalonic  ester, 

C2H5OCH  =  C(C02C2H5)2, 

in   alkaline   solution,   condenses   normally   with   ethylpseudo- 
thiourea,     H2N — C(SC2H5)=NH,     giving    2-ethylmercapto-5- 

1  THIS  JOURNAL,  37,  392  (1907). 


Researches  on  Pyrimidines.  595 

carbethoxy-6-oxypyrimidine  (I.).  We  now  find  that  this 
cyclo  amide  reacts  smoothly  with  phosphorus  oxychlorider 
yielding  an  oil  which  is  the  imide  chloride,  2-ethylmercapto- 
5-carbethoxy-6-chlorpyrimidine  (!!.)•  The  transformation  of 
this  into  2-ethylmercapto-5-carbethoxy-6-aminopyrimidine 
(III.),  on  standing  with  alcoholic  ammonia  at  ordinary  tem- 
perature, is  also  a  perfectly  smooth  reaction.  The  imide 
chloride,  therefore,  in  this  case,  is  far  more  reactive  than  2-ethyl- 
mercapto-6-chlorpyrimidine.  The  latter  does  not  react  on 
standing  overnight  with  alcoholic  ammonia,  but  it  does  react 
in  a  short  time  at  120°. 

When  the  mercaptoamino  ester  (III.)  is  heated  with  alcoholic 
ammonia  the  mercapto  group  is  the  first  to  be  removed  (at 
about  170°)  and  2,6-diamino-5-carbethoxypyrimidine  (IV.) 
results. 

When  the  mercaptoamino  ester  (III.)  is  carefully  warmed 
with  dilute  alcoholic  potassium  hydroxide  it  is  readily  saponi- 
fied and  a  potassium  salt  of  2-ethylmercapto-5-carboxyl-6- 
amino-pyrimidine  (V.)  is  formed.  If  the  treatment  with 
potassium  hydroxide  is  more  energetic,  mercaptan  is  also  re- 
moved and  the  potassium  salt  of  cytosine-5-carboxylic  acid 
is  obtained  (VI.). 

The  moderate  action  of  strong  hydrochloric  acid  on  2-ethyl- 
mercapto-5-carbethoxy-6-aminopyrimidine  (III.)  first  removes 
ethylmercaptan,  giving  5-carbethoxycytosine  (VII.),  which 
with  aqueous  ammonia  at  150°  is  partially  converted  into  cy- 
tosine-5-carboxamide  (VIII.). 

Longer  boiling  with  hydrochloric  acid  saponifies  the  ester 
(III.),  both  mercaptan  and  alcohol  separate,  and  cytosine-5- 
carboxylic  acid  (VI.)  results.  The  synthesis  of  the  acid  and 
the  transformations  of  the  new  pyrimidines  can  be  illustrated 
by  the  formulas  on  page  596. 

The  action  of  acids  on  cytosine-5-carboxylic  acid  (VI.) 
developed  the  interesting  fact  that  the  presence  of  the  carboxyl 
radical  in  the  5 -position  rendered  the  amino  group  apparently 
more  easily  subject  to  hydrolysis  than  in  the  case  of  unsub- 
stituted  cytosine.  It  was  found  also  that  the  6-amino  group 
was  removed  before  the  carboxyl  radical  when  cytosine-5- 


596 


Wheeler  and  Johns. 


a   5- 
fc    x- 


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W     o 


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8 

0—0  = 


—  o— 
O 


—  o— 


W 

lri 


w 


fc 
rf 


w 

o  8- 

I      o     W 


tf    5 


W 


1*4 


5- 


o — o=< 


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ffl 


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wow 


Researches  on  Pyrimidines.  597 

carboxylic  acid  was  boiled  with  20  per  cent  sulphuric  acid, 
the  chief  product  obtained  being  uracil-5-carboxylic  acid  (IX.), 
while  only  a  small  amount  of  cytosine  was  formed.  Unless 
groups  attached  to  cytosin-5-carboxylic  acid  would  alter  the 
course  of  hydrolysis,  these  results  exclude  the  possibility  that 
cytosin  exists  in  the  nucleic  acids  in  the  form  of  a  5-carboxyl 
derivative,  or,  in  other  words,  it  is  not  a  grouping  of  this  sort 
which  is  the  source  of  cytosine. 

Further  action  of  acids,  either  at  a  high  temperature,  or 
on  more  prolonged  boiling,  strips  all  of  the  groups  from  the 
above  compounds,  leaving  uracil  (X.)  as  the  last  pyrimidine 
to  be  obtained. 

EXPERIMENTAL  PART. 

2-  Eihylmercapto-5-carbethoxy-6-chlor pyrimidine, 
N=CCl 
I  | 

C,H6SC  CCOaC2H6.— Thirteen  grams  of  2-ethyl-mercapto- 

N CH 

5-carbethoxy-6-oxypyrimidine  were  boiled  for  two  and  a  half 
hours  with  40  cc.  of  phosphorus  oxychloride.  The  phosphorus 
oxychloride  was  then  removed  by  evaporation  at  100°  under 
diminished  pressure.  This  left  a  syrup  which  was  treated 
with  cracked  ice  and  the  resulting  oil,  which  did  not  solidify, 
was  extracted  with  ether  and  dried  over  calcium  chloride. 
It  boiled  at  203  °  at  20  mm.  pressure.  The  yield  of  oil  is  almost 
quantitative  and  the  crude  product  is  pure  enough  to  use  for 
the  following  preparations  without  distilling.  Nitrogen  de- 
terminations in  the  case  of  the  distilled  product  gave: 

Calculated  for  Found. 

C9Hai02NsSCl.  I.  II. 

N  11.35  11.33  11.31 

2-Ethylmercapto-5-carbethoxy-6-aminopyrimidine, 
N :C— NH2 

I  I 

C2H5SC  CCO2C,H6. — Fourteen  grams  of  2-ethylmercapto- 

N CH 

5-carbethoxy-6-chlorpyrimidine  were  added  to  a  cold  saturated 


598  Wheeler  and  Johns. 

solution  of  alcoholic  ammonia  in  a  bottle.  A  reaction  set  in 
almost  at  once  and  a  mass  of  crystals  separated.  The  bottle 
was  kept  cool  by  means  of  ice-  water.  The  material  was 
allowed  to  stand  overnight  and  then  the  alcohol  and  ammonia 
were  evaporated  and  the  residue  treated  with  water.  The  yield 
was  90  per  cent  of  the  calculated.  The  resulting  product 
melted  to  an  oil  in  hot  water  but  did  not  dissolve.  It  dis- 
solved readily  in  hydrochloric  acid.  It  was  easily  soluble  in 
hot  and  moderately  soluble  in  cold  alcohol  from  which  solvent 
it  crystallized  in  rectangular  plates  melting  at  102°.  Analysis: 

Calculated  for  Found. 

I.  II. 


N  18.50  18.41  18.42 

When  this  substance  was  boiled  with  strong  hydrochloric  acid 
for  about  one  hour,  the  solution  evaporated  to  dryness  and  the 
residue  dissolved  in  sodium  hydroxide  and  precipitated  with 
acetic  acid,  cytosine-5-carboxylic  acid  was  obtained. 

N=  =C—  NH2 

I  I 

2,6-Diamino-5-carbethoxypyrimidine,  H2N  —  C          CCO2C2H5. 

N  -  CH 

—  This  was  obtained  by  heating  the  above  2-ethylmercapto-5- 
carbethoxy-6-aminopyrimidine  with  a  saturated  solution  of 
alcoholic  ammonia  at  1  68°-  178°  for  one  and  a  half  hours. 
When  the  tube  became  cool,  a  solid  separated.  The  material 
was  difficultly  soluble  in  cold  alcohol  and  water  and  it  crystal- 
lized from  alcohol  in  the  form  of  needles  melting  to  a  clear 
oil  at  205°-2O7°.  Analysis: 

Calculated  for  Found. 

C7H1002N4.  I.  II. 

N  30.76  30.62  30.76 

This  substance  is  soluble  in  hydrochloric  acid  from  which  solu- 
tion it  is  reprecipitated  by  ammonia.  The  material  which  re- 
mained in  the  alcoholic  mother-liquor  from  the  above  was 
found  to  be  unaltered  mercapto-derivative.  Under  the  con- 
ditions of  the  experiment  it  appears  that  the  carbethoxy  group 
was  not  attacked. 


Researches  on  Pyrimidines.  599 

2-Ethylmercapto-5-carboxyl-6-aminopyrimidine, 
N=C— NH2 
I  | 

C2H5SC          CCOOH  .—When   2-ethylmercapto-5-carbethoxy- 

N CH 

6-aminopyrimidine  in  alcoholic  solution  was  treated  with  an 
equal  weight  of  potassium  hydroxide  in  a  small  amount  of 
water  it  was  readily  saponified.  On  evaporating  to  dryness 
the  resulting  residue  dissolved  easily  in  water.  When  this 
solution  was  made  acid  with  acetic  acid  a  white  crystalline 
substance  slowly  separated.  This  was  slightly  soluble  in  hot 
water  and  difficultly  soluble  in  hot  alcohol,  from  which  it  crys- 
tallized in  microscopic  prisms.  It  decomposed  with  efferves- 
cence at  230°.  It  was  very  soluble  in  ammonia  and  also  in 
an  excess  of  hydrochloric  acid.  Analysis : 

Calculated  for  Found. 

C7H9OjN3S.  I.  II. 

N  21.10  2095  21.04 

During  the  above  hydrolysis  there  was  a  decided  odor  of  es- 
caping mercaptan.  In  order  to  determine  whether  mercaptan 
could  be  conveniently  split  off  by  means  of  potassium  hydrox- 
ide, another  portion  of  2-ethylmercapto-5-carbethoxy-6-amino- 
pyrimidine  was  heated  a  little  longer  on  the  steam-bath  with 
somewhat  more  than  2  molecular  proportions  of  potassium  hy- 
droxide. On  acidifying  the  residue,  a  substance  was  obtained 
which  did  not  contain  sulphur  and  agreed  in  properties  with 
cytosine-5-carboxylic  acid.  (Analysis  III.  below.) 

N- C—  NH, 

Cytosine-5-carboxylic  Acid,OC          CCOOH . — This  amino  acid 

I!         II 

HN CH 

was  first  prepared  by  evaporating  the  above  mercaptoamino 
acid  with  concentrated  hydrochloric  acid  on  the  steam-bath. 
After  evaporating  once  with  a  moderate  amount  of  acid,  the 
residue  was  taken  up  in  water  and  evaporated  again  to  remove 
hydrochloric  acid.  It  was  found  that  the  acid  was  almost  in- 
soluble in  hot  water,  alcohol  and  acetic  acid.  The  specimen 


6oo  Wheeler  and  Johns. 

used  for  analysis  was  purified  by  dissolving  in  ammonia  and 
precipitating  with  acetic  acid.  It  came  down  in  a  very  finely 
divided  state  and  was  hard  to  filter.  It  decomposed  with 
effervescence  at  2 56° '-257°.  Analysis: 

Calculated  for  Found. 

C6H508lsr8.  I.  II.  in. 

N  27.09  27.07        27.07        26.80 

To  prepare  this  acid  it  is  not  necessary  to  isolate  the  2-ethyl- 
mercapto-5-carboxyl-6-aminopyrimidine.  The  easiest  way  is 
to  start  with  2-ethylmercapto-5-carbethoxy-6-aminopyrimidine 
and  evaporate  this  once  with  an  equal  weight  of  potassium  hy- 
droxide in  dilute  alcohol.  Concentrated  hydrochloric  acid  is 
then  added  to  the  residue  and  the  evaporation  carried  on  again 
to  dryness.  The  mixture  is  taken  up  in  water,  to  remove 
potassium  chloride,  and,  on  filtering  and  washing  with  water, 
the  acid  is  obtained  in  an  almost  pure  condition.  The  aqueous 
solution  of  cytosine-5-carboxylic  acid  does  not  give  a  precip- 
itate with  barium  chloride,  picric  acid  or  lead  acetate.  It  gives 
but  a  slight  turbidity  with  silver  nitrate. 

Action  of  Twenty  Per  Cent  Sulphuric  Acid:  Formation 
of  UracU-5'Carboxylic  Acid.  —  One  gram  of  cytosine-5-car- 
boxylic  acid  was  boiled  on  a  return  condenser  for  20  hours 
with  40  cc.  of  sulphuric  acid.  A  solid  separated  on  cooling. 
It  weighed  0.5  gram.  This  was  crystallized  from  water  and 
came  down  in  clusters  of  pointed,  microscopic  prisms  which 
decomposed  at  277°.  They  were  indentified  as  uracil-5-car- 
boxylic  acid.  Analysis:  0.3133  gram  substance  lost  0.0329 
gram  water  at  I2O°-I3O°. 

Calculated  for 

C6H404N2.HsO.  Found. 

H,O  10.34  10.50 

N  17-94  l8.22 

A  duplicate  experiment  performed  as  above  gave  0.45  gram 
of  uracil-5-carboxylic  acid,  which  separated  from  the  solution. 
After  filtering  from  this,  the  sulphuric  acid  was  removed  and 
the  solution  concentrated  to  10  cc.,  then  precipitated  with 
picric  acid.  This  gave  0.17  gram  picrate,  crystallizing  in 
needles,  equal  to  0.06  gram  cytosin. 

Formation  of  Uracil. — One  half  gram  of  cytosine-5-carbox- 


Researches  on  Pyrimidines.  60 1 

ylic  acid  was  heated  with  5  cc.  of  20  per  cent  sulphuric  acid  at 
i62°-i67°  for  2  hours.  On  opening  the  sealed  tube,  consid- 
erable pressure  was  noticed  and  a  deposit  which  had  the  ap- 
pearance of  uracil  had  separated.  This  was  recrystallized 
from  water  and  identified  as  uracil.  Analysis: 

Calculated  for 
C4H4OjN2.  Found. 

N  25.00  24.97 

Action  of  Concentrated  Hydrochloric  Acid:  Formation  of 
Uracil. — One  gram  of  cytosine-5-carboxylic  acid  was  boiled 
with  50  cc.  of  concentrated  hydrochloric  acid,  using  a  return 
condenser,  for  22  hours.  The  acid  was  then  evaporated  and 
the  residue  was  treated  with  boiling  water.  A  small  portion 
was  insoluble  in  hot  water.  This  was  unaltered  cytosine-5- 
carboxylic  acid;  an  analysis  gave  26.80  per  cent  of  nitrogen 
while  the  calculated  is  27.09  per  cent. 

The  portion  which  was  soluble  in  water  crystallized  in  balls 
like  uracil.  Analysis  gave  24.90  per  cent  nitrogen. 

Cytosine-j-carboxylic  Acid  Hydrochloride  was  prepared  by 
crystallizing  some  of  the  acid  from  20  per  cent  hydrochloric 
acid.  It  formed  ragged  pointed  prisms  which  melted  at  275°- 
276°  and  it  contained  a  molecule  of  water  of  crystallization. 

Analysis : 

0.1327  gram  lost  0.0117  gram  of  water  at  130°- 140°. 

Calculated  for 
C6H6O8N8.HC1.H,O.  Found. 

HaO  8.59  8-82 

Calculated  for 

C6H6O3N8.HC1.  Found. 

N  21.93  21.71 

N C— NH, 

I  I 

5-Carbethoxycytosine,   OC          CCO2CaH6,     was    formed     by 

HN CH 

evaporating  2-ethylmercapto-5-carbethoxy-6-aminopyrimidine 
with  concentrated  hydrochloric  acid  on  the  steam  bath.  The 
product  was  dissolved  in  hot  water  and  the  solution  after 
making  slightly  alkaline  with  ammonia  gave  needles  which 


602  Wheeler  and  Johns. 

browned  and  decomposed  slowly  at  about  26o°-275°.     This 
ester  was  only  slightly  soluble  in  hot  alcohol.     Analysis: 


Calculated  for  Found. 

C7H9O3N8.  I.  II. 


N  22.95  22.97  23.00 

N=  =C— NH. 

I  I 

Cytosine-5-carboxamide,   OC  CCONH,.— The   action    of 

HN CH 

concentrated  aqueous  ammonia  on  the  above  ester  was  not  at 
all  smooth.  In  one  experiment  in  which  the  ester  was  heated 
with  concentrated  ammonia  for  2  hours  at  140°- 150°,  about 
25  per  cent  of  the  material  remained  unaltered  but  on  evapora- 
ting the  mother-liquor  far  more  soluble  material  was  obtained. 
This  crystallized  in  tufts  of  hair-like  needles.  It  was  recrystal- 
lized  from  water.  (Analysis  I.)  On  heating,  no  definite  melt- 
ing or  decomposition  point  was  observed. 

Analyses  of  two  different  samples  gave  the  following  results 
which  show  that  the  expected  amide  had  been  obtained. 

Calculated  for  Found. 

C6H602N4.  I.  II. 

N  36.36  35-94  35-00 

NEW  HAVBN,  COWN., 
May,  1907. 


[Reprinted  from  the  American  Chemical  Journal,  Vol.  XXXVIII. 
No.  5.    November,  1907.] 


CL.— RESEARCHES  ON  PYRIMIDINES:  SYNTHESIS  OF 
THYMINE-5'-CARBOXYLIC  ACID. 

[TWENTY- SEVENTH  PAPER.] 

BY  TREAT  B.  JOHNSON  AND  CARL  FRANK  SPEH. 

The  possibilty  that  uracil,  cytosine  and  thymine  might 
be  linked  in  nucleic  acids  by  acid  amide  or  polypeptide  group- 
ings was  an  incentive  to  make  a  thorough  study  of  the  car- 
boxyl  derivatives  of  these  pyrimidines.  Descriptions  of 
uracil-5-carboxylic  acid,1  I.,  thymine-4-carboxylic  acid,2  IV., 
cytosine-5-carboxylic  acid,3  III.,  and  uracil-4-carboxylic  acid,4 

1  Wheeler,  Johnson  and  Johns:  THIS  JOURNAL,  37,  392. 

2  Johnson:  Jour.  Biolog.  Chem.,  3,  299. 

3  Wheeler  and  Johns:  THIS  JOURNAL,  38,  594. 

4  Wheeler:  Ibid.,  38,  358. 


Researches  j)n  Pyrimidines.  603 

II.,  have  already  been  published  in  papers  from  this  laboratory. 
NH CO  NH CO  N=  :=CNH, 

II  I  J  II, 

CO       CCOOH,        CO        CH        ,         CO        CCOOH 

II!  I          II  I         II 

NH CH  NH CCOOH          NH CH 

I.  II.  III. 

NH CO  NH CO 

I  I  I      --II 

CO        CCH3     ,  CO   .*  CCH2COOH. 

I          II  I        Ml 

NH CCOOH  NH CH 

IV.  V. 

We  shall  describe  in  this  paper  the  preparation  and  proper- 
ties of  thymine-5'-carboxylic  acid,  V.  The  carbon  atom  in 
the  methyl  radical  of  thymine  is  designated  5'  in  order  to  avoid 
confusion  and  to  distinguish  from  position  7  in  the  purine 
molecule.  We  find  that  this  acid,  V., 


L* JL^I  '     \ 

&/* 


Pyrimidine.  Purine. 

can  be  heated  with  20  per  cent  sulphuric  acid  at  i6o°-i7O° 
without  alteration.  Thymine,  therefore,  cannot  exist  in  nucleic 
acids  as  a  j'-carboxyl  compound. 

The  information  acquired  by  investigating  these  pyrimidine 
acids  has  advanced  decidedly  our  knowledge  of  the  structure 
of  the  nucleic  acid  "molecule.  The  results  of  our  work  justify 
us  in  concluding  that  uracil  is  the  only  one  of  the  three  pyr- 
imidines— uracil,  cytosine  and  thymine— that  can  be  linked 
in  nucleic  acids  by  an  acid  amide  grouping — CO.NH.  Uracil 
might  exist  as  a  $-carboxyl  compound.  This  conclusion  is  sup- 
ported by  the  fact  that  uracil-5-carboxylic  acid,1  I.,  is  quan- 
titatively converted  into  uracil  when  heated  with  20  per  cent 
sulphuric  acid  at  i6o°-i7o°.  Uracil-4-carboxylic  acid,1  IL, 
and  thymine-4-carboxylic  acid,1  IV.,  could  be  heated  under 

i  Loc.  cti. 


604  Johnson  and  Speh. 

the  same  conditions  without  alteration.  The  possibility  of 
cytosine  being  linked  as  a  5-carboxyl  compound  is  excluded, 
since  cytosine-5-carboxylic  acid,1  III.,  is  changed  to  uracil- 
5-carboxylic  acid  by  hydrolysis  with  dilute  sulphuric  acid. 

Every  a-derivative  of  ethyl  /?-oxyacrylate  (et  hylf ormyl- 
acetate)  that  we  have  examined  in  this  laboratory  has  con- 
densed with  a  pseudothiourea,  in  presence  of  alkali,  giving  a 
2-mercapto  pyrimidine,  viz. : 

1.  Ethyl  /?-oxyacrylate,2 

HOCH:CH.COOC2H5. 

2.  Ethyl  a-methyl-/?-oxyacrylate,8 

HOCH :  C(CH3)COOC2H5. 

3.  Ethyl  a-phthalimido-/?-oxyacrylate,4 

/C 

HOCH:  C(N< 

XCO' 

4.  Ethyl  a-benzoylamino-/?-oxyacrylate,5 

HOCH:  C(NHCOC8H5)COOC2H6. 

5.  Ethyl  a-phenyl-/9-oxyacrylate,fl 

HOCH :  C(C8H5)COOC2H6. 

6.  Ethyl  a-urethane-/?-oxyacrylate,7 

HOCH:  C(NHCOOC2H5)COOC2H5. 

7.  Ethyl  a-ethoxy-/?-oxyacrylate,8 

HOCH :  C(OC2H5)COOC2H5. 

8.  Ethyl  a-ethyl-/?-oxyacrylate,9 

HOCH :  C(C2H5)COOC2H5. 

9.  Ethyl  a-phenoxy-/?-oxyacrylate,10 

HOCH :  C(OC8H5)COOC2H5. 

1  Loc.  ctt. 

*  Wheeler  and  Merriam:  THIS  JOURNAL,  29,  478. 
»  Wheeler  and  Merriam:  Loc.  cit. 

4  Johnson  and  Clapp:  THIS  JOURNAL,  32,  130. 

*  Johnson  and  Clapp:  Loc.  eft. 

6  Wheeler  and  Bristol:  THIS  JOURNAL,  33,  448. 

7  Johnson:  Ibid.,  34,  191. 

•Johnson  and  McCollum:  Jour.  Biolog.  Chem.,  1,  437.     THIS  JOURNAL,  36,  149; 
9  Johnson  and  Menge:  Jour.  Biolog.  Chem.,  2,  105. 
M  Johnson  and  Heyl:  THIS  JOURNAL,  37,  628. 


Researches  on  Pyrimidines.  605 

We  now  find  that  the  sodium  salt  of  diethyl  formylsuccin- 
ate  condenses  in  a  smooth  manner  with  pseudoethylthio- 
urea,  giving  ethyl  2-ethylmercapto-6-oxypyrimidine-5-ace- 
tate,  VI.  The  condensation  is  represented  by  the  following 
equation : 

NH2  COOCaH6 


C        +      CCH3COOC8H6    = 

II  II 

NH       HOCH 


NH CO 

I 


H,0  +  CaH6OH  +  C3H6SC          CCH3COOC,Hft. 

II  II 

N CH 

VI. 

When  ethyl  2-ethylmercapto-6-oxypyrimidine-5-acetate,  VI., 
was  digested  with  concentrated  hydrochloric  acid,  or  with 
alcohol  and  hydrochloric  acid,  it  was  converted  quantitatively 
into  thymine-5'-carboxylic  acid,  VIII.  Esterification  of  thymine- 
5'-carboxylic  acid  with  ethyl  alcohol  and  sulphuric  acid  gavethy- 
mine-5'-ethylcarboxylate,  IX.  2-Ethylmercapto-6-oxypyrimi- 
dine-5-acetic  acid ,  VII.,  was  obtained  when  ethyl  2-ethylmercap- 
to-6-oxypyrimidine-5-acetate,  VI.,  was  saponified  with  an  alco- 
holic solution  of  potassium  hydroxide.  When  this  mercapto 
acid  was  digested  with  hydrochloric  acid  it  was  converted 
into  thymine-5'-carboxylic  acid. 

Ethyl  2-ethylmercapto-6-oxypyrimidine-5-acetate,  VI.,  re- 
acts in  a  smooth  manner  with  phosphorus  oxychloride,  giving 
2-ethylmercapto-6-chlorpyrimidine-5-acetic  acid,  X.  When 
the  mercapto  ester,  VI.,  was  heated  with  ammonia  it  was  con- 
verted into  2-ethylmercapto-6-oxypyrimidine-5-acetamide,  XL, 
and  2-amino-6-oxypyrimidine-5-acetamide,  XII.  These  differ- 
ent transformations  are  represented  by  the  formulas  on  the 
following  page. 

Thymine-5'-carboxylic  acid  is  difficultly  soluble  in  water 
and  melts  at  about  the  same  temperature  as  thymine  (315°- 
320°).  It  crystallizes  from  water  in  anhydrous  condition. 
It  is  a  strong  acid  and  gives  an  insoluble,  crystalline  lead  salt, 


6o6 


Johnson  and  Speh. 


8-8  =g 
I        Id 

B-8-g 


ffi 

£ 
o 

q 

w 

o    o 


f 


— <J=i 


W 


W  M 

^;—  0==^; 

§ 


w 


T 


H     o 

2;—  o 


O     5     B 

^ro=cf,- 
i 


K 

I 

0    5 


S 


§ 

8 


8-B=S 


w 


5- 


w 

1 

8-8  =3 


X 


2-0=^ 


5 


Researches  on  Pyrimidines.  607 

when  lead  acetate  is  added  to  its  aqueous  solution.  It  was 
not  precipitated  by  phosphotungstic  acid.  Addition  of  barium 
chloride  to  aqueous  solutions  of  the  acid  produced  no  pre- 
cipitate. Potassio-bismuth  iodide  gave  a  yellow,  crystalline 
precipitate. 

EXPERIMENTAL   PART. 

Diethyl  Formylsuccinate,    CHO.CH.COOC2H5.—  The  sodium 


salt  of  this  ester  was  prepared  by  condensing  ethyl  formate 
with  diethyl  succinate  in  presence  of  metallic  sodium.  Eleven 
grams  of  sodium  wire  were  suspended  in  anhydrous  ether  and 
a  mixture  of  molecular  proportions  of  ethyl  formate  and  di- 
ethyl succinate  slowly  added.  There  was  an  immediate  re- 
action with  evolution  of  hydrogen  gas  and  the  ether  assumed 
a  red  color.  The  mixture  was  allowed  to  stand  for  ten  to 
twelve  hours  and  then  shaken  with  cold  water  to  dissolve  the 
sodium  salt  of  diethyl  formylsuccinate.  When  this  aqueous 
solution  was  acidified  with  hydrochloric  acid  the  free  ester 
separated  as  a  heavy  yellow  oil.  After  drying,  in  ether  solu- 
tion with  calcium  chloride  it  was  distilled  under  diminished 
pressure.  The  fraction  that  was  analyzed  boiled  at  158°- 
160°  under  20  mm.  pressure. 

I.  0.4614  gram  substance  gave  0.8994  gram  CO2  and  0.2816 
gram  H2O. 

II.  0.5762  gram  substance  gave  1.1107  grams  CO2  and  0.3573 
gram  H2O. 

Calculated  for  Found. 

Q,H1404.  I.  II. 

C  53-4  53.i6  52.58 

H  6.93  6.79  6.89 

Ethyl  2-Ethylmercapto-  6-oxypyr  imidine-  5-  acetate, 
NH  -  CO 

I  I 

C3H6SC          C.CH3COOCaH5.—  One    hundred    and    sixty-five 

II  II 
N  -  CH 

grams  of  diethyl  succinate  and  one  molecular  proportion  of 
ethyl  formate  were  condensed  in  presence  of  the  required 


608  Johnson  and  Speh. 

amount  of  metallic  sodium,  as  described  in  the  previous  ex- 
periment. The  sodium  salt  of  diethyl  formylsuccinate 
was  then  dissolved  in  cold  water  and  added  to  an  aqueous 
solution  of  109  grams  of  pseudoethylthiourea  hydrobromide. 
A  molecular  proportion  of  potassium  hydroxide  was  then 
added  and  the  mixture  allowed  to  stand  for  seven  to  eight 
hours  at  ordinary  temperature.  It  was  then  heated  on  the 
steam-bath  for  three  hours  and  cooled,  when  prismatic  crys- 
tals of  the  mercapto  pyrimidine  deposited.  When  the  alka- 
line solution  was  acidified  with  acetic  acid,  more  of  the  pyr- 
imidine separated.  The  compound  was  practically  insolu- 
ble in  cold  water,  but  dissolved  in  boiling  water  and  separated, 
on  cooling,  in  well  developed,  prismatic  crystals.  It  crys- 
tallized from  alcohol  in  slender  needles  melting  at  i46°-i47°, 
with  no  effervescence.  It  crystallized  from  water  without 
water  of  crystallization.  The  yield  of  crude  pyrimidine  was 
80  grams.  Analysis  (Kjeldahl)  : 

Calculated  for  Found. 

I.  II. 


N  11-57  1  1.  60  H-55 

In  two  other  experiments  we  obtained  22  grams  and  38 
grams  of  the  mercapto  pyrimidine  from  63  grams  and  90  grams 
of  diethyl  succinate,  respectively. 

2-Ethylmercapto-  6-  oxy  pyrimidine-  $-acetic  A  cid, 
NH  -  CO 


I 
C 


.CH2COOH.—  This  acid  was  prepared  by  saponi- 


N  ---  CH 

fying  the  ethyl  ester  with  potassium  hydroxide.  Ten  grams 
of  the  ester  and  3  grams  of  potassium  hydroxide  were  digested 
in  alcohol  for  about  twelve  hours.  The  alkaline  solution  was 
then  evaporated  to  dryness  and  the  residue  obtained  dissolved 
in  warm  water.  This  solution  was  then  acidified  with  acetic 
acid,  when  about  i  gram  of  unaltered  ester,  melting  at  146°, 
separated.  After  evaporating  the  filtrate  to  dryness  and  dis- 
solving the  residue  again  in  a  little  water,  the  solution  was 
acidified  with  a  few  drops  of  dilute  hydrochloric  acid.  The 


Researches  on  Pyrimidines.  609 

mercapto  acid  separated  at  once  and  crystallized  from  hot 
water  in  needles  and  square  plates  melting  at  184°,  with  evo- 
lution of  carbon  dioxide  and  ethylmercaptan.  When  di- 
gested with  hydrochloric  acid  it  was  converted  into  thymine- 
5'-carboxylic  acid  (see  below).  Analysis  (Kjeldahl): 

Calculated  for  Found. 

C8H1003N2S.  I.  II. 

N  13.08  12.9  12.85 

NH CO 

I  I 

The  Potassium   Salt,    C2H6SC  CCH2COOK.— This    salt 

II  II 
N CH 

was  extremely  soluble  in  water  and  alcohol.  It  separated 
from  very  concentrated,  aqueous  solutions  in  long  needles. 
They  did  not  contain  water  of  crystallization.  Analysis 
(Kjeldahl) : 

Calculated  for 
C8H903N2SK.  Found. 

N  ii. ii  11.31 

2-Ethylmercapto-  6-chlor pyrimidine- 5- acetic  A  cid 
N iCCl 

C2H6SC  C.CH2COOH.— Ethyl  2-ethylmercapto-6-oxypyr- 


imidine-5-acetate  dissolves  at  once  in  cold  phosphorus  oxy- 
chloride,  with  no  evolution  of  heat.  Fifteen  grams  of  the 
pyrimidine  were  dissolved  in  50  cc.  of  phosphorus  oxychloride 
and  the  solution  boiled  gently  for  two  and  a  half  hours.  It  was 
then  allowed  to  stand  for  five  to  six  hours  and  poured  upon 
crushed  ice  to  destroy  the  excess  of  phosphorus  halides.  We 
obtained  a  dark  colored  solution,  which  was  extracted  several 
times  with  ether.  This  ether  solution  was  then  thoroughly 
washed  with  sodium  hydroxide  solution  and  the  alkaline  wash- 
ings saved.  When  they  were  neutralized  with  hydrochloric 
acid  the  chlorpyrimidine  separated  in  granular  crystals.  The 
yield  was  8.5  grams.  The  pyrimidine  was  difficultly  soluble 


6io  Johnson  and  Speh. 

in  water  and  very  soluble  in  alcohol.  It  crystallized  from 
alcohol  in  clusters  of  prismatic  crystals,  melting  at  132°,  to 
a  clear  oil.  When  heated  above  its  melting  point  it  decom- 
posed with  violent  effervescence.  Analysis  (Kjeldahl): 

Calculated  for  Found. 

I.  II. 


N  12.07  n-9  12.  02 

Action  of  Alcoholic  Ammonia  on  Ethyl  2-Ethylmercapto-6- 
oxy  pyrimidine-  5-acetate.  —  Two  grams  of  the  pyrimidine  and 
25  cc.  of  alcoholic  ammonia  were  heated  for  two  hours  at  140°— 
150°.  When  the  tube  was  opened  there  was  no  pressure  but 
there  was  a  strong  odor  of  ethyl  mercaptan.  We  obtained  a 
deposit  of  crystalline  material,  which  was  very  soluble  in  hot 
water  and  separated,  on  cooling,  in  prismatic  crystals  associa- 
ted with  some  needles.  By  a  fractional  crystallization  from 
water  we  finally  separated  a  compound  which  melted  at  214°, 
with  slight  effervescence.  It  responded  to  a  test  for  sulphur 
and  a  nitrogen  determination  agreed  with  the  calculated 
value  in 

2-  Ethylmercapto-6-oxy  pyrimidine-  5-acetamide, 
NH  -  CO 

C2H5SC          CCH2CONH2  .— 


Calculated  for 
C8HuOaNsS.  Pound. 

N  19.75  19.58 

In  a  second  experiment,  4  grams  of  the  mercapto  ester 
and  50  cc.  of  alcoholic  ammonia  were  heated  for  two  hours 
at  I7o°-i8o°.  When  the  tube  was  examined  there  was  no 
pressure  but  a  strong  odor  of  mercaptan,  and  small,  granular 
crystals  were  suspended  in  the  alcohol.  These  were  removed 
and  recrystallized  from  water.  On  cooling,  prismatic  crys- 
tals separated,  which  charred  at  26o°-266°  and  then  decom- 
posed at  about  280°,  with  violent  effervescence.  They  did 
not  respond  to  a  test  for  sulphur  and  a  nitrogen  determina- 
tion agreed  with  the  calculated  value  in 


Researches  on  Pyrimidines.  611 


2-  A  mino-  6-oxypyrimidine-^-acetamide, 
NH CO 


NH2C          CCH2CONH2.— 


Calculated  for  Found. 

CoH8OaN4.  I.  II. 

32.6  32.75 

NH CO 

|  I 

Thymine-5'-carboxylicAcid,  CO        C.CH2COOH.— This  acid 

NH CH 

was  obtained  when  ethyl  2-ethylmercapto-6-oxypyrimidine- 
5-acetate  was  digested  in  alcoholic  solution  with  hydrochloric 
acid.  Five  grams  of  the  mercapto  ester  were  dissolved  in  a 
mixture  of  20  cc.  of  alcohol  and  5  cc.  of  concentrated  hydro- 
chloric acid  and  the  solution  heated  on  the  steam-bath  for 
2.5  hours.  The  pyrimidine  separated  as  a  colorless,  crystal- 
line powder  that  was  practically  insoluble  in  alcohol.  A 
quantitative  yield  of  the  acid  was  also  obtained  when  ethyl 
2  -  ethylmercapto  -  6  -  oxypyrimidine  -  5  -  acetate  or  2-ethylmer- 
capto-6-oxypyrimidine-5-acetic  acid  was  digested  with  con- 
centrated hydrochloric  acid  (Analyses  IV.  and  V.).  Analysis 
(Kjeldahl) : 

Calculated  for  Found. 

C9H604N2.  I.  II.  III.  IV.  V. 

N        16.47  16.28     16.12     16.28     16.5     16.5 

Thymine-5'-carboxylic  acid  was  very  insoluble  in  cold  water 
but  crystallized  from  boiling  water  in  microscopic,  granular 
crystals,  which  generally  melted  at  3i5°-32O°,  with  decompo- 
sition. It  did  not  contain  water  of  crystallization,  and  when 
mixed  with  thymine  the  melting-point  was  lowered  to  290°- 
300°.  Its  aqueous  solution  gave  a  strong  acid  reaction  when 
tested  with  blue  litmus.  It  was  precipitated  by  silver  nitrate 
and  mercuric  chloride  in  weak  ammoniacal  solutions.  The 
silver  salt  dissolved  in  excess  of  ammonia.  Copper  carbonate 
was  decomposed  by  the  acid,  giving  an  insoluble  copper  salt. 
Barium  chloride  does  not  precipitate  a  barium  salt  from 


6  12 


Johnson  and  Speh. 


aqueous  solutions  of  the  acid.  The  acid  was  not  precipitated 
by  phosphotungstic  acid,  but  potassio-bismuth  iodide  gave  a 
yellow,  granular  precipitate. 

Solubility  in  Water  at  30°.  —  One  hundred  parts  water  dis- 
solved 

i.  n. 

o  .  3566  part  acid  o  .  4038  part  acid 

NH  --  CO 

I  I 

The  Potassium  Salt,    CO        CCH2COOK.iH2O.—  This  salt 

I  II 

NH  -  CH 

was  very  soluble  in  water  and  was  prepared  by  dissolving 
the  acid  in  water  containing  the  required  amount  of  potas- 
sium hydroxide.  It  crystallized  from  a  concentrated  aqueous 
solution  in  prismatic  crystals  containing  water  of  crystalliza- 
tion. The  water  was  determined  by  heating  for  one  and  a 
half  hours  at  io5°-ii5°. 

0.8947  gram  substance  lost  0.0307  gram  H2O. 


H2O 


Calculated  for 
4N2 

4.1 


Found. 

3.45 


Nitrogen  determination  in  the  anhydrous  salt  (Kjeldahl)  : 

Calculated  for  Pound. 


The  Lead  Salt, 


13-45 
~NH- 

CO 
NH- 


I. 

I3-58 


II. 

13-47 


o 


CCH2CO2 

II 
-CH 


2Pb.iH2O  or 


This  was  a  very  characteristic  salt  and  separated,  at  once,  when 
lead  acetate  was  added  to  a  hot,  saturated,  aqueous  solution 
of  thymine-5'-carboxylic  acid.  It  was  more  insoluble  than 
the  acid  and  crystallized  from  boiling  water  in  rhombic  tables. 
It  contained  water  of  crystallization,  which  was  determined 
by  heating  for  two  hours  at  iio°-ii5°. 
0.3103  gram  salt  lost  0.0122  gram  H2O. 


Researches  on  Pyrimidines.  613 

Calculated  for 
(C«Hi04N2)aPb.H20.     (CftH^NzkPb.iiH^.  Found. 


H,O  3.19  4-6  3-93 

Nitrogen  determination  in  the  anhydrous  salt  (Kjeldahl)  : 

^Calculated  for 

(C8H5O4N8)2Pb.  Pound. 

N  10.28  10.32 

Action  of  20  Per  Cent  Sulphuric  Acid  on  Thymine-^'-car- 
boxylic  Acid.  —  One  gram  of  the  acid  was  heated  with  10  cc. 
of  sulphuric  acid  for  two  hours,  at  I5o°-i6o°.  There  was  no 
pressure  when  the  tube  was  opened  and  the  acid  had  crys- 
tallized from  the  acid  solution  in  prismatic  crystals.  They 
melted  at  3i5°-32o°,  with  decomposition,  and  when  mixed 
with  thymine  the  decomposition  point  was  lowered  below 
300°.  Analysis  (Kjeldahl)  : 

Calculated  for  Pound. 

CeHeO4N2.  I.  II. 

N  16.47  16.5  16.6 

In  a  second  experiment,  3  grams  of  thymine-5'-carboxylic 
acid  were  heated  with  30  cc.  of  20  per  cent  sulphuric  acid  for 
ten  hours,  at  i6o°-i7o°.  We  observed  practically  no  decom- 
position under  these  conditions  and  the  acid  was  recovered 
unaltered,  melting  at  3i5°-32o°.  Analysis  (Kjeldahl): 

Calculated  for 
QjH604N2.  Found. 

N  16.47  16.35 

NH  -  GO 

[  I 

Thymine-  5f-ethylcarboxylate,  CO        CCH2COOC2H6,  was  pre- 

NH  -  CH 

pared  in  the  usual  manner  by  esterifying  the  acid  with  abso- 
lute alcohol  and  concentrated  sulphuric  acid.  It  crystallized 
from  boiling  alcohol  in  rectangular  plates  melting  at  204°- 
210°,  according  to  the  rate  of  heating.  Analysis  (Kjeldahl): 

Calculated  for  Pound. 

C8H1004N8.  I.  II. 

N  14-14  13-7  13-9 

NEW  HAVEN,  CONN., 
July  4,  1907. 


[Reprinted  from  the  American  Chemical  Journal,  Vol.  XXXVIII. 
No.  6.    December,  1907.] 


Contributions  fr,pm  the  Sheffield  Laboratory  of  Yale  University. 

CUV.— RESEARCHES  ON  PYRIMIDINES :  SYNTHESIS  OF 
4-METHYUJRACIL-5-ACETIC  ACID. 

[TWENTY-EIGHTH  PAPER.] 

BY  TREAT  B.  JOHNSON  AND  FREDERICK  W.  HEYL. 

It  was  shown,  in  a  previous  paper  from  this  laboratory,1 
that  diethyl  formylsuccinate  condenses  smoothly  with  pseudo- 
ethylthiourea,  giving  ethyl  2-ethylmercapto-6-oxypyrimidine-5- 
acetate  (I.).  When  this  pyrimidine  was  warmed  with  concen- 
trated hydrochloric  acid,  it  was  converted  quantitatively  into 
thymine-5'-carboxylic  acid  (II.) : 


C2H 


NH  --  CO 

I 
SC 


N 


CCHoCOOC2He 

II 
-CH 


I. 

Johnson  and  Speh:  THIS  JOURNAL,  38,  602. 


NH CO 

I  I 

CO         CCH2COOH, 

I  II 

NH CH 

II. 


660  Johnson  and  Heyl. 

(1)  4-Methyluracil~5-acetic  acid  can  be  prepared  in  an  anal- 
ogous manner  from  pseudoethylthiourea  and  diethyl  acetosuc- 
cinate.1     They  condense,  in  presence  of  an  excess  of  alkali, 
giving  a  good  yield  of   2-ethylmercapto-4-methyl-6-oxypyrimi- 
dine-5-acetic  acid  (III.)«     The  condensation  can  be  represented 
by  the  following  equation : 

NH3  COOC2H6 

C2H5SC       +  CCH2COOC2H5     = 

II  II 

NH          HO.CCH8 

NH CO 

I  I 
2C.H5OH  +  C2H5SC          CCH2COOH. 

II  II 

N CCH3 

III. 

It  is  an  interesting  fact  that  the  mercapto  acid  (III.)  is  obtained 
in  this  condensation,  instead  of  the  ethyl  ester,  as  in  the  con- 
densation with  diethyl  formylsuccinate. 

(2)  Ethylmercapto  -4-  methyl  -6-  oxypyrimidine  -5-  acetic  acid 
(III.)    was    quantitatively    converted    into    4-methyluracil-5- 
acetic  acid  (VI.)  when  digested  with  concentrated  hydrochloric 
acid.     When  an  alcoholic  solution  of  the  mercapto  acid  (III.) 
was  boiled  with  a  small  quantity  of  hydrochloric  acid  a  mixture 
of    ethyl    2-ethylmercapto-4-methyl-6-oxypyrimidine-5~acetate 
(IV.)   and  ethyl  4-methyluracil- 5 -acetate   (V.)   was  obtained. 
The  latter  ester    was    also    formed    by  esterifying   the    oxy- 
gen acid  (VI.)  with  ethyl  alcohol  and   sulphuric  acid.     2-Am- 
ino-4-methyl-6-oxypyrimidine-5-acetic  acid  (VII.)  was  prepared 
by  heating  2-ethylmercapto-4-methyl-6-oxypyrimidine-5-  acetic 
acid  (III.)  with  alcoholic  ammonia. 

2-Ethylmercapto-4-methyl-6-oxypyrimidine-5-acetic  acid  re- 
acts smoothly  with  phosphorus  oxychloride,  giving  2-ethyl- 
mercapto-4-methyl-6-chlorpyrimidine-5-acetylchloride  (VIII). 
This  acid  chloride  was  decomposed  immediately  by  cold  water, 
giving  2  -ethylmercapto-4-methyl-6-chlorpyrimidine-5-acetic 
acid  (XI.).  2-Ethylmercapto-4-methyl-6-chlorpyrimidine-5-acet- 

1  Fittig  and  Spencer:  Ann.  Chem.  (Liebig),  283,  67. 


Researches  on  Pyrimidines.  66 1 

amide  (IX.)  was  formed  when  the  acid  chloride  was  poured 
into  cold  alcoholic  ammonia. 

2-Ethylmercapto  -4-  methyl  -6-  chlorpyrimidine  -5-  acetic  acid 
(XI.)  is  very  stable  in  the  presence  of  ammonia.  It  was  re- 
covered unaltered  after  heating  with  alcoholic  ammonia  at  120°. 
Treatment  with  ammonia  at  i35°gave  2-ethylmercapto-4-methyl- 
6-aminopyrimidine-5-acetic  acid  (XII.).  When  heated  with 
alcoholic  ammonia  at  I7o°-i8o°  the  mercapto  radical  was 
also  replaced  by  the  amino  group  and  2,6-diamino-4-methyl- 
pyrimidine-5-acetic  acid  (X.)  resulted.  These  different  trans- 
formations are  represented  by  the  formulas  on  page  662. 

4-Methyluracil-5-acetic  acid  (VI.)  is  less  soluble  in  water 
than  the  thymine^'-carboxylic  acid  (II.)  described  by  Johnson 
and  Speh.1  It  gives  characteristic  potassium,  barium,  and 
lead  salts  which  crystallize  from  water  with  water  of  crystal- 
lization. The  acid  is  not  precipitated  from  its  aqueous  solu- 
tion by  barium  chloride  or  phosphotungstic  acid.  It  can  be 
heated  with  20  per  cent  sulphuric  acid  at  153°- 173°  without 
alteration. 

EXPERIMENTAL  PART. 

2-Methylmercapto-4-methyl-6-oxypyrimidine-<5-acetic  A cid, 
NH CO 

CH3SC          CCH2COOH. 

i!          II 

N CCH, 

Ten  grams  of  pseudomethylthiourea  hydriodide  were  dis- 
solved in  water  and  10  grams  of  diethyl  acetosuccinate  and  5 
grams  of  potassium  hydroxide  added  to  the  solution.  The  mix- 
ture was  then  allowed  to  stand  for  8-10  hours  at  ordinary  tem- 
perature and  then  warmed  on  the  steam  bath  to  complete  the 
reaction.  After  cooling,  the  solution  was  acidified  with  hy- 
drochloric acid,  when  the  mercapto  derivative  deposited  in 
prisms.  It  crystallized  from  hot  water  or  alcohol  in  flat  prisms 
that  sintered  at  260°  and  then  decomposed  at  27O°-272°  with 
effervescence.  Analysis  (Kjeldahl) : 

1  Loc.  cit. 


662 


w 

o  S 

0—0  = 


g      O      W 

£  —  O—  J2J 


Johnson  and  Heyl. 


tg 

8 

"JU 


5 


§ 

o 
o 


W 


B 

cJ 

o" 
o 

ft  uC 

H     o 
-0=0 


5  °  e 

^—  o—  ^ 


a 

o 
o 


°_  0^=1 


o 

1 


ft 

CJ 


o 

o 

4,    . 

o     o     o 
0—0=0 


w 

o" 


o     o     o 
0—0=0 


I 


H 

.§ . 

U-8 


Researches  on  Pyrimidines.  663 

Calculated  for  Found. 

C8H10O3NoS.  I.  II. 

N                 13.08  13.14  13-06 

2-Ethylmercapto-4-methyl-  6-oxy  pyrimidine- ^-acetic  A  cidt 
NH CO 


CCH2COOH. 


CCH3 


The  best  yield  of  this  pyrimidine  was  obtained  when  we  pro- 
ceeded under  the  following  conditions:  Thirty-five  grams  of 
the  hydrobromide  of  pseudoethylthiourea  were  dissolved  in 
about  250  cc.  of  cold  water  and  43  grams  of  diethyl  acetosuc- 
cinate  stirred  into  the  solution.  Twenty-two  grams  of  potas- 
sium hydroxide  were  then  added,  when  a  clear  solution  resulted. 
This  was  then  allowed  to  stand  overnight  at  ordinary  tempera- 
ture and  finally  heated  on  the  steam  bath  for  one  hour.  After 
cooling  and  shaking  with  ether  to  remove  any  unaltered  diethyl 
acetosuccinate,  an  excess  of  acetic  acid  was  added,  when  the 
mercaptopyrimidine  deposited  in  granular,  prismatic  crystals. 
The  yield  was  19  grams,  corresponding  to  about  72  per  cent 
of  the  theoretical.  In  a  second  condensation  we  obtained  4.2 
grams  of  the  mercaptopyrimidine  from  8  grams  of  the  pseudo- 
urea  hydrobromide  and  10  grams  of  diethyl  acetosuccinate. 
This  pyrimidine  is  practically  insoluble  in  cold,  and  sparingly 
soluble  in  hot,  water.  It  deposited  from  boiling  95  per  cent 
alcohol  in  blocks.  It  dissolved  in  boiling  benzonitrile  and 
nitrobenzene  and  separated  from  both  of  these  solvents,  on 
cooling,  in  elongated  prisms.  The  decomposition  point  varies 
with  the  rate  of  heating,  but  it  usually  decomposed  at  about 
255  °>  evolving  carbon  dioxide  and  ethylmercaptan.  Analysis 
(Kjeldahl) : 

Calculated  for  Found. 

CgHjaOaNoS.  I.  II. 

N  12.28  12.55  12.30 

Potassium  Salt,  C9HnO3N2SK.— This  salt  is  extremely  soluble 
in  cold  water.  It  crystallized  from  50  per  cent  alcohol  in  mi- 
croscopic needles.  Analysis  (Kjeldahl): 


664  Johnson  and  Heyl. 


Calculated  for  Found. 

I.  II. 


N  10.52  10.67  IO-45 

Ethyl  2-  Ethylmercapto-4-methyl-6-oxypyrimidine-  ^-acetate, 
NH  -  CO 

I  I 

C2H6SC          CCH2COOC2H6. 

II  II 

N  -  CCH8 

This  ester  was  not  obtained  as  a  product  of  the  preceding  con-  ! 
densation.  This  is  explained  by  the  fact  that  it  was  necessary 
to  use  an  excess  of  potassium  hydroxide  to  keep  the  diethyl 
acetosuccinate  in  solution  and  the  ester,  if  formed,  was  always 
saponified.  It  was  prepared  by  boiling  the  mercapto  acid  in 
alcoholic  solution  with  a  few  drops  of  sulphuric  acid.  Two  grams 
of  the  mercapto  acid,  25  cc.  of  absolute  alcohol,  and  2  cc.  of 
concentrated  sulphuric  acid  were  digested  on  the  steam  bath 
for  5  hours.  The  excess  of  alcohol  was  then  evaporated  at 
ordinary  temperature,  when  we  obtained  an  oily  residue  with 
some  colorless,  prismatic  crystals  in  suspension.  These  were 
filtered  by  suction  and  the  syrup  again  allowed  to  stand  for  a 
few  hours,  when  a  second  crop  was  obtained.  The  yield  was 
0.25  gram  and  the  compound  was  identified  as  4-methyluracil-5- 
ethylacetate  (see  below).  The  syrup  was  treated  with  20-30 
cc.  of  cold  water,  when  a  crystalline  compound  deposited  which 
melted  at  1  5  1  °-i  63  °  to  a  clear  oil.  It  deposited  from  95  per  cent 
alcohol  in  hairlike  crystals  that  melted  at  i63°-i65°  to  a  clear 
oil.  It  gave  a  test  for  sulphur.  Analysis  (Kjeldahl)  : 

Calculated  for  Found. 

CnH1608N2S.  I.  II. 

N  10.93  I][-4  11.08 

4-Methyluracil-  ^-acetic  Acid, 
NH  -  CO 

I  I 

CO        CCH2COOH. 

I  II 

NH  -  CCHS 

2-Ethylmercapto-4-methyl-6-oxypyrimidine-5-acetic  acid  dis- 
solves at  once  in  cold,  concentrated  hydrochloric  acid  and  the 


Researches  on  Pyrimidines.  665 

solution  can  be  evaporated  to  dryness  on  the  steam  bath  and 
the  acid  recovered  unaltered.     A  quantitative  yield  of  the  oxy- 
gen acid  was  obtained,  nevertheless,  by  boiling  the  mercapto- 
jyrimidine  with  concentrated  hydrochloric  acid  until  the  evo- 
.ution  of    ethylmercaptan    ceased.      It    deposited    from    the 
[boiling  acid  solution  as  a  heavy,  granular  powder.     The  acid 
I  is  practically  insoluble  in  boiling  alcohol  and  insoluble  in  cold 
(water.     It  crystallized  from  hot  water  in  long,  transparent 
|  prisms  that  sintered  at  about  329°  and  decomposed  at  340° 
(Anschiitz  thermometer)  with  violent  effervescence.     Bromine 
j  does  not  react  with  the  acid  in  acetic  acid  solution  at  ordinary 
temperature.     Analysis : 

I.  o.  1950  gram  of  substance  gave  0.3274  gram  of  CO2  and 
10.0787  gram  of  H2O. 

II.  0.2352  gram  of  substance  gave  0.3935  gram  of  CO2  and 
0.0955  gram  of  H2O.     Nitrogen  (Kjeldahl): 

Calculated  for  Found. 

C7H8O4N,.  I.  II.  III.  IV. 

C        45.65  45-77     45-62 

4-34  4 • 48       4-50     

N         15.21  l5-<>9     I5-!0 

Solubility  in  Water  at  25°. — One  hundred  grams  of  water 

dissolved : 

i.  ii. 

0.0901  gram  acid  0.0894  gram  acid 

Potassium  Salt  of  4- Methyluracil- ^-acetic  Acid,  C7H?O4N2K 
3H2O,  was  prepared  by  dissolving  the  acid  in  water  with 
one  molecular  proportion  of  potassium  hydroxide.  The  salt 
was  extremely  soluble  in  water  but  crystallized  from  very- 
concentrated  solutions  in  prismatic  crystals.  They  contained 
water  of  crystallization  which  was  determined  by  heating  the 
salt  at  io5°-i25°  for  5  hours. 

o. 8455  gram  of  the  salt  lost  o.  1544  gram  H2O. 

Calculated  for 
C7H7O4N2K.3HaO.  Found. 

H2O  19.5  18.26 


Nitrogen  determination  for  anhydrous  salt  (Kjeldahl) : 

Calculated  for 
C7H7O4N2K.  Found. 

N  12.60  12.42 


666  Johnson  and  Heyl. 

Silver  Salt  of  4- Methyluracil- ^-acetic  Acid,  C7H?O4N2Ag. — 
When  the  potassium  salt  described  above  was  dissolved  in 
water  and  a  molecular  proportion  of  silver  nitrate  added,  a 
gelatinous  silver  salt  deposited.  It  was  insoluble  in  boiling 
water  and  did  not  assume  a  crystalline  form.  Analysis  for 
silver : 

Calculated  for 

C7H7O4N2Ag.  Found. 

Ag  37.11  40.00 

Barium  Salt  of  ^Methyluracil-^-acetic  Acid,  (C7H?O4N2)2 
Ba.H2O. — When  the  calculated  proportions  of  the  acid  and 
barium  chloride  were  dissolved  in  hot  water  and  the  solution 
cooled,  the  unaltered  acid  separated.  The  salt  was  prepared 
by  dissolving  the  potassium  salt  in  water  and  adding  the  cal- 
culated amount  of  barium  chloride.  The  salt  separated,  on 
cooling,  in  small  prisms  which  were  dried  for  analysis  in  a  des- 
iccator over  sulphuric  acid.  It  contained  one  molecule  of 
water  of  crystallization  which  was  determined  by  heating  for 
2  hours  at  uo°-i36°. 

0.8114  gram  of  salt  lost  0.0300  gram  of  H2O. 

Calculated  for 
(C7H7O4N2)2Ba.H2O.  Found. 

H2O  3.45  3-69 

Nitrogen  determination  for  anhydrous  salt  (Kjeldahl) : 

Calculated  for 

(C7H7O4N2)2Ba.  Found. 

N  11.12  11.05 

Lead  Salt  of  4- Methyluracil- ^-acetic  Acid,  (C7H7O4N2)2Pb. 
H2O. — This  salt  was  obtained  as  an  insoluble  crystalline 
powder  when  lead  acetate  was  added  to  a  solution  of  the  acid. 
It  crystallized  from  water  in  glistening  plates  or  flat  prisms 
which  were  dried  for  analysis  in  a  desiccator  over  sulphuric 
acid.  It  contained  one  molecule  of  water  of  crystallization 
which  was  determined  by  heating  at  117°- 125°  for  4  hours. 

1.2847  grams  of  salt  lost  0.0377  gram  H2O. 

Calculated  for 
(C7H7O4N2)2Pb.H2O.  Found. 

H2O  3.04  2.93 


Researches  on  Pynmidines.  667 

Analysis  of  the  anhydrous  salt  : 

0.2594  gram  substance  gave  0.2769  gram  CO2  and  0.0583 
gram  H2O.     Nitrogen  (Kjeldahl)  : 

Calculated  for  Found. 

I.  II.  III. 


C  29.32  29.12         ....          .... 

H  2.44  2.49         ........ 

N  9.77  10.00         9.73 

Action  of  20  Per  Cent  Sulphuric  Acid.  —  The  acid  was  recovered 
unaltered  after  heating  with  sulphuric  acid  for  2  hours  at 
I53°-I73°.  When  crystallized  from  water  it  decomposed  at 
340°.  Analysis  (Kjeldahl)  : 

Calculated  for  Found 

C7H8O4N2.  I.  II.  III. 

N  15.21  15.31         15.32         15.17 

Ethyl  Ester  of  4.-  Methyluracil-  ^-acetic  Acid, 
NH  -  CO 

CO        C.CH2COOC2H5. 

I  II 

NH  -  CCH3 

This  ester  was  obtained  as  a  secondary  product  when  we  ester- 
ified  2-ethylmercapto-4-methyl-6-oxypyrimidine-5-acetic  acid. 
It  was  easily  obtained  in  pure  condition  by  esterifying  the  oxy- 
gen acid  in  the  usual  manner.  It  crystallized  from  95  per  cent 
alcohol  in  needles  that  melted  at  2  2  1  °-2  2  2  °  to  a  clear  oil.  Anal- 
ysis (Kjeldahl): 

Calculated  for 

a.  Found. 


N  13.20  13.12 

Methyl  Ester  of  4-  Methyluracil-  5-  acetic  Acid, 

NH  -  CO 

I  I 

CO        CCH2COOCH3. 

I  II 

NH  --  CCH3 

This  ester  deposited  from  methyl  alcohol  in  fine  needles  that 
decomposed  at  28o°-282°.     Analysis  (Kjeldahl): 


668  Johnson  and  Heyl. 

Calculated  for  Found. 

C8Hio04N2.  i.  II. 

N  H-H  14.10  14.4 

2- A  mino-4-methyl-  6-oxypyrimidine- ^-acetic  A  cid, 

NH CO 

I  I 

NH,C  CCH7COOH. 


Four  grams  of  2-ethylmercapto-4-methyl-6-oxypyrimidine-5- 
acetic  acid  were  heated  with  alcoholic  ammonia  for  4  hours 
at  1 70°- 1 80°.  When  the  tube  was  opened  there  was  some 
pressure,  and  the  odor  of  ethylmercaptan  was  apparent.  The 
solution  was  evaporated  to  dryness  and  the  crystalline  residue 
purified  by  recrystallization  from  water.  It  deposited  in  needles 
that  decomposed  at  322°  with  effervescence.  Analysis  (Kjel- 
dahl) : 

Calculated  for  Found. 

C7H9O3N3.  I.  II. 

N  22.95  23.3  23.2 

2-EthylmercaptO"4-methyl-  6-chlorpyrimidine- ^-acetic  A  cid , 
N CC1 

C2H6SC          CCH,COOH. 


Ten  grams  of  2-ethylmercapto-4-methyl-6-oxypyrimidine-5- 
acetic  acid  and  50  cc.  of  phosphorus  oxychloride  were  warmed  on 
the  steam  bath  until  the  evolution  of  hydrochloric  acid  gas 
practically  ceased  (2  hours).  A  dark  colored  solution  was  ob- 
tained. This  was  slowly  poured  upon  crushed  ice  to  decompose 
the  excess  of  phosphorus  oxychloride.  No  insoluble  material 
deposited  after  this  treatment,  but  when  the  acid  solution  was 
neutralized  with  sodium  hydroxide  the  chloride  separated  in 
slender  needles  which  dissolved  again  when  an  excess  of  alkali 
was  added.  The  chloride  was  soluble  in  boiling  benzene  but 
insoluble  in  cold  benzene ;  very  soluble  in  alcohol.  It  was  puri- 
fied for  analysis  by  recrystallization  from  hot  water  and  depos- 


Researches  on  Pyrimidines.  669 

• 

ited  in  needles  that  melted  at  ii8°-ii9°  with  evolution  of 
carbon  dioxide.     The  yield  was  good.     Analysis   (Kjeldahl)  : 


Calculated  for  Found. 

.  II. 


N  11.35  n-53  11-56 

2-Ethylmercapto-4-methyl-6-chlorpyrimidine-5-acetamide, 
N  -  CC1 

C,H5SC          CCH2CONH2. 

II  II 

N  -  CCH8 

2-Ethylmercapto-4-methyl-6-oxypyrimidine-5-acetic  acid  was 
digested  with  an  excess  of  phosphorus  oxychloride  until  the 
evolution  of  hydrochloric  acid  gas  ceased.  Instead  of  being 
poured  into  water  as  in  the  previous  experiment,  this  solution 
was  poured  slowly  into  a  large  volume  of  cold,  alcoholic  ammonia. 
The  excess  of  alcohol  and  ammonia  was  then  evaporated  and 
the  residue  triturated  with  cold  water  to  dissolve  ammonium 
chloride.  We  obtained  a  crystalline  compound  that  was  insol- 
uble in  cold  water  but  crystallized  from  hot  water  in  sheaves 
that  decomposed  at  167°.  The  compound  was  very  soluble 
in  hot  alcohol  but  can  be  crystallized  from  50  per  cent  alcohol 
and  from  benzene.  It  was  insoluble  in  dilute  sodium  hydroxide 
solution.  Analysis  (Kjeldahl)  : 

Calculated  for  Found. 

C9H12ON3SC1.  I.  II. 

N  17.10  17.5  17.4 

Action  of  Alcoholic  Ammonia  on  2-Ethylmercapto-4-methyl-6- 
chlorpyrimidine-  ^-acetic  Acid.  —  The  mercaptopyrimidine  was 
recovered  unaltered  after  heating  with  strong,  alcoholic  am- 
monia for  2  hours  at  85  °—  95  °  and  again  for  3  hours  at  i  io°—  120°. 

Action  at  12  5°-i35°  '•  Formation  of  2-Ethylmercapto-4-methyl-6- 
aminopyrimidine-  $-acetic  Acid, 

N-  -  CNH2 

I  I 

C2H5SC          CCH2COOH. 

II  II 

N  -  CCH3 


67o  Johnson  and  Heyl. 

Two  and  five-tenths  grams  of  the  chloride  were  heated  with 
alcoholic  ammonia  for  2.5  hours  at  125  °-i35  °.     When  the  tube 
was  opened  there  was  some  pressure  and  a  small  amount  of 
colorless,  crystalline  material  was  suspended  in  the  alcohol. 
This  was  identified  as  the  ammonium  salt  of  2-ethylmercapto-4- 
methyl-6-aminopyrimidine-5-acetic   acid.     The   free   acid   was 
obtained  by  triturating  the  salt  with  dilute  acetic  acid.     It  de- 
posited from  95  per  cent  alcohol  in  beautiful  needles  that  melted 
sharply  at  221°.     They  gave  tests  for  sulphur  and  chlorine. 
This  reaction  was  not  smooth  and  the  yield  of  the  amino  deriv- 
ative was  poor.     When  the  alcoholic  filtrates  were  evaporated 
to  dryness  a  crystalline   residue  deposited.     This  proved  to 
be  a  mixture  from  which  nothing  sufficiently  pure  for  analysis 
was  isolated.     Analysis  (Kjeldahl)  : 

Calculated  for 
CgHjgOsNgS.  Found. 

18.50  18.64 


2 


,  6-Diamino-4-methylpyrimidine-5-acetic  A  rid, 

N=:CNH2 

NH2C          CCH2COOH. 


This  base  was  prepared  by  heating  2-ethylmercapto-4-methyl-6- 
chlorpyrimidine-5-acetic  acid  with  alcoholic  ammonia  for  2  hours 
at  i67°-i8o°.  When  the  tube  was  opened  there  was  much 
pressure,  and  a  crystalline  compound  had  deposited  from  the 
alcohol.  This  crystallized  from  hot  water  in  small  prismatic 
crystals  that  melted  at  279°-28o°  with  effervescence,  turning 
brown  at  about  270°.  It  did  not  give  tests  for  sulphur  and 
chlorine,  and  dissolved  in  alkali  and  acids.  Analysis  (Kjeldahl) : 

Calculated  for 

C7HioO2N4.  Found. 

N  30.77  30.61 

NEW  HAVEN,  CONN., 
July  6,  1907. 


VIII.     RESEARCHES  ON  PYRIMIDINS :  A  METHOD  OF 
SEPARATING  THYMIN  FROM  URACIL. 

(Twenty-ninth  Paper.) 
BY  TREAT  B.  JOHNSON. 

(From  the  Sheffield  Laboratory  of  Yale  University.) 
(Received  for  publication,  March  28,  1908). 

New  data  about  the  cleavage  products  of  nucleic  acids  con- 
tribute to  our  knowledge  of  the  constitution  of  these  acids. 
Practical  analytical  methods  for  the  quantitative  determination 
of  the  products  of  hydrolysis  are  of  the  greatest  importance. 
Kossel  and  his  co-workers  have  developed  excellent  methods 
for  determining  the  purin  bases — xanthin,  guanin,  adenin  and 
hypoxanthin.  On  the  other  hand,  methods  for  separating  quan- 
titatively the  pyrimidins  are  lacking.  A  delicate  qualitative  test 
for  uracil  and  cytosin,  in  presence  of  thymin,  has  been  described 
in  a  publication  from  this  laboratory,1  but  at  present  there  is 
no  test,  or  characteristic  derivative  known,  which  serves  for  the 
identification  of  thymin  in  presence  of  uracil.  For  its  detection 
we  make  use  of  the  sublimation,  the  behavior  towards  silver 
nitrate  and  its  elementary  analysis. 

A  careful  review  of  the  nucleic  acid  literature  reveals  the  fact 
that  several  investigations,  in  this  field,  signify  the  necessity 
of  a  practical  method  of  separating  thymin  from  uracil.  Kut- 
scher2  in  an  investigation  on  the  autolysis  of  thymus  glands 
isolated  0.6  gram  of  a  crystalline  substance  whose  properties 
corresponded  with  those  of  thymin,  but  whose  content  of  nitro- 
gen did  not  agree  with  the  theoretical  value.  He  found  23.4 
and  24.1  per  cent  of  nitrogen  while  the  calculated  value  for  thy- 
min is  22.22  per  cent.  His  views  are  summarized  in  his  own 
words:  "Diese  Reactionen  der  Krystalle  sowie  ihr  Verhalten 
gegen  ammoniakalische  Silberlosung  sprachen  fur  Thymin,  doch 

1  Wheeler  and  Johnson:     This  Journal,  iii,  p.   183. 

2  Zeitschr.  f.  physiol.  Chem.,  xxxiv,  p.  114. 

407 


408  Separation  of  Thymin  from  Uracil 

bestatigte  die  Analyse  diese  Voraussetzung  nicht  vollig.  Auch 
durch  vielfache  Umkrystallization  und  andere  Reinigungsver- 
suche  Hess  sich  dieser  Sticks t off werth  nicht  herunterdrucken.  Es 
musste  also  dem  Thymin  eine  stickstoff  reichere  Substanz  viel- 
leicht  Uracil  beigemengt  sein." 

Steudel1  in  an  investigation  on  the  hydrolysis  of  thymus  nucleic 
acid  with  hydriodic  acid  isolated  5.9330  grams  of  a  substance 
which  gave  23.38  per  cent  of  nitrogen  on  analysis.  He  says: 
"Als  die  Flussigkeit  jetzt  eingeengt  wurde,  schied  sich  ein  Ge- 
menge  von  Thymin  und  Uracil  aus,  das  ich  in  Ermangelung  einer 
guten  Trennungsmethode  nicht  weiter  aufgeteilt,  sondern  als 
solches  analysiert  habe."  He2  also  obtained  a  mixture  of 
thymin  and  uracil  in  a  later  investigation  on  the  oxidation  of 
nucleic  acid  with  nitric  acid.  In  a  recent  paper,  entitled  "Die 
Zusammensetzung  der  Nucleinsauren  aus  Thymus  und  aus 
Heringssperma,"  Steudel3  wrote:  "Der  nach  der  Krystallization 
der  alloxurbasen  noch  bleibende  Rest  lieferte  weiterer  Behand- 
lung  Thymin  und  Uracil.  Diese  beiden  Korper  liessen  sich  durch 
fraktionierte  Krystallization  zwar  nicht  quantitativ  aber  doch 
qualitativ  gut  trennen." 

I  shall  describe  in  this  paper  a  new,  characteristic  derivative 
of  thymin,  and  a  method  of  separating,  practically  quantitatively 
thymin  from  uracil. 

Uracil  and  thymin  do  not  react,  below  100°,  with  nitric  acid 
of  density  1.41.  On  the  other  hand  uracil  dissolves,  at  ordinary 
temperature,  in  fuming  nitric  acid  of  density  1.5  giving  practically 
a  quantitative  yield  of  5 -nitro uracil  I.  Thymin  reacts,  under  the 
same  conditions,  giving  a  quantitative  yield  of  the  addition 
product — oxynitrohydrothymin*  1 1 . 

NH  —  CO  NH  —  CO 

I            I                      HN03  |  | 

CO        CH  >  CO         CNO2 

I  I!  I          II 

NH  —  CH  NH  —  CH 

I 

1  Zeitschr.  f.  physiol  Chem.,  xlii,  p.  169. 

*Ibid.t  xlviii,  p.  425. 

8  Ibid.,  liii,  p.   14. 

4  Johnson:  Amer.  Chem.  Journ.     (To  be  published  in  vol.  xl.) 


Treat  B.  Johnson  409 

XCH3 


NH  —  CO  NH  —  CO 

|  |  HN03  | 

CO       CCH3  --  >  CO 


NH  —  CH  NH  —  CHOH 

II 

In  a  paper,  entitled  "Die  Constitution  des  Thymins,"1  Steudel 
has  described  the  action  of  concentrated  nitric  acid  on  thymin. 
He  obtained  a  compound  to  which  he  assigned  the  empirical  for- 
mula, C4H4O3N4.  He  gave  no  melting  point  for  the  compound, 
but  states  that  it  did  not  contain  water  of  crystallization  ;  that 
it  was  soluble  in  warm  water  and  ammonia  and  gave,  on  reduc- 
tion, a  derivative  which  responded  to  Weidel's  alloxan  reaction. 
The  data  which  I  have  obtained2  seem  to  indicate  that  Steu- 
del's  nitrothymin  was  a  secondary  decomposition  product  and 
not  a  simple  thymin  derivative. 

The  formation  of  the  hydropyrimidin  II,  involves  a  direct 
addition  of  nitric  acid  to  the  double  bond  between  the  four  and 
five  positions  of  the  pyrimidin  ring.  Oxynitrohydrothymin  II, 
exists  in  two  modifications  which  I  have  designated  by  the  Greek 
letters  a  and  /?.  The  two  isomers  are  formed  under  practically 
the  same  conditions.  The  a-derivative  is  the  stable  modification 
and  melts  at  183°  to  185°.  The  /^-derivative  melts  at  230°  to 
235°  and  rearranges  to  the  a-form  at  the  ordinary  temperature. 
These  isomeric  oxynitrohydrothymins  are  especially  characterized 
by  their  crystalline  habit,  and  are  converted  quantitatively  into 
thymin  by  reduction  with  tin  and  hydrochloric  acid. 

5-Nitrouracil  and  Oxynitrohydrothymin  show  a  remarkable 
difference  in  solubility  in  cold,  absolute  ethyl  alcohol.  The  hydro- 
pyrimidin is  extremely  soluble  in  this  reagent,  while  5-nitrouracil 
requires  approximately  800  to  900  parts  of  cold  alcohol  for  com- 
plete solution.  I  have  devised  a  simple  method  of  separating 
thymin  from  uracil  by  the  use  of  this  difference  in  solubility  in 
alcohol.  The  mixture  of  uracil  and  thymin  is  treated  with  the 
proper  proportions  of  fuming  nitric  acid  (sp.  gr.  1.5)  and  con- 
verted into  5-nitrouracil  and  Oxynitrohydrothymin  respectively. 

1  Zeitschr.  /.  physiol.  Chem.,  xxxii,  p.  241. 

2  Loc.  cit. 


4io  Separation  of  Thymin  from  Uracil 

The  conditions  of  this  operation  are  described  in  detail  in  the 
experimental  part  of  this  paper.  The  hydrothymin  is  then 
separated  from  nitrouracil  by  trituration  with  absolute  alcohol. 
The  hydrothymin  can  be  identified  by  its  melting  point  and  crys- 
talline habit.  Furthermore  the  thymin  can  be  recovered  by 
reduction  of  the  hydropyrimidin  with  tin  and  hydrochloric  acid. 
The  nitrouracil  is  identified  by  elementary  analysis  and  reduction 
to  5-aminouracil1  with  aluminum  amalgam.  This  base  gives 
a  characteristic  picrate  which  melts  at  24y°.2 

The  Action  of  Nitric  Acid  on  Thymin. 

Nitric  Acid  (sp.  gr.  1.415):  Five-tenths  of  a  gram  of  thymin 
was  dissolved  in  2  cc.  of  concentrated  nitric  acid  and  the  solution 
evaporated  to  dryness  on  the  steam  bath.  There  was  no  evidence 
of  any  reaction  and  the  thymin  was  recovered  unaltered.  It 
deposited  from  hot  water  in  plates  that  decomposed  at  about 
321°.  When  mixed  with  pure  thymin  this  decomposition  point 
was  not  lowered.  Analysis  (Kjeldahl) : 

Calculated  for 
C.,H«O2N2:  Found : 

N 22.22  22.33 

Nitric  Acid  (sp.  gr.  1.5):  The  Formation  of  a-Oxynitrohydro- 
thymin : 

NH  —  CO 
I  I     /N02 

CO         C< 
I  XCH3 

NH  — CH.OH 

Thymin  dissolves  in  cold,  fuming  nitric  acid  with  slight  evolution 
of  heat.  If  red  fumes  are  evolved  by  this  treatment  it  is  an 
indication  that  the  thymin  is  not  pure.  The  hydropyrimidin 
was  obtained  perfectly  pure,  and  the  yield  was  quantitative, 
when  thymin  was  treated  with  fuming  nitric  acid  under  the 
following  conditions:  One  gram  of  thymin  was  dissolved  in  6  cc. 
of  nitric  acid  and  the  solution  allowed  to  evaporate  at  ordinary 
temperature.  The  nitropyrimidin  deposited  in  large,  well-de- 

1  Behrend  and  Griinwald:  Ann.  d.  Chem.,  cccix,  p.  256. 

2  Wheeler  and  Bristol:  Anter.  Chem.  Journ.,  xxxiii,  p.  437. 


Treat  B.  Johnson  411 

veloped  prisms  or  blocks  (see  figure)  which  decrepitated  above 
130°  and  melted  at  183°  with  violent  effervescence.  The  com- 
pound was  soluble  in  hot  water,  extremely  soluble  in  alcohol, 
and  separated  from  both  these  solvents  in  blocks  that  melted 
at  183°  to  185°.  It  was  insoluble  in  benzene.  The  pyrimidin 
did  not  lose  weight  after  drying  for  1.5  hours  at  100°  to  110° 
and  again  for  one-half  hour  at  1 10°  to  115°.  When  heated  above 
120°  it  slowly  underwent  decomposition.  The  composition  of 
the  compound  was  not  altered  by  recrystallization  from  absolute 
alcohol  (Analysis  III) : 

0.2086  gram  substance  gave  0.2454  gram  CO2  and  0.0695  gram  H2O. 
Nitrogen  determinations  (Kjeldahl) : 

Calculated  for  Calculated  for  Found: 

C5H7O5N3:         C5H6O2N2  (Thymin):  I.  II.  III. 

C 31.74  47.61  32.08 

H 3.70  4.76  3.70 

N '          22.22  22.22  22.00       21.95 

a-Oxynitrohydrothymin  dissolves  in  water  giving  an  acid 
reaction.  The  pyrimidin  undergoes  decomposition  when  its 
aqueous  solution  is  boiled.  The  addition  of  barium  hydroxide 
to  its  aqueous  solution  produces  no  precipitate  or  color.  No 
thymin  deposited  when  an  alcoholic  solution  of  the  pyrimidin 
was  treated  with  ammonia.  When  the  nitropyrimidin  was  dis- 
solved in  concentrated  sulphuric  acid,  and  a  few  drops  of  ferrous 
sulphate  solution  added,  the  characteristic  test  for  nitric  acid 
was  obtained. 

a-Oxynitrohydrothymin  can  also  be  prepared  by  dissolving 
thymin  in  fuming  nitric  acid  (1.5)  and  evaporating  the  solution 
to  dryness,  at  once,  on  the  steam  bath.  This  method  of  nitration 
can  be  recommended  for  preparing  quickly  small  quantities  of 
the  hydropyrimidin.  The  yields  are  not  quantitative  since  part 
of  the  thymin  undergoes  oxidation.  The  best  results  are 
obtained  by  this  method,  when  i  gram  portions  of  thymin  are 
nitrated  under  the  following  conditions:  One  gram  of  thymin 
is  dissolved  in  4  cc.  of  nitric  acid  (1.5)  and  the  solution  evaporated 
to  dryness,  at  100°,  as  quickly  as  possible.  The  nitrothymin  is 
obtained  as  a  colorless,  crystalline  residue  which  crystallizes 
from  water  in  blocks  decomposing  at  183°  to  185°.  It  is  possible, 
in  this  manner,  to  prepare  several  grams  of  the  hydropyrimidin 


412 


Separation  of  Thymin  from  Uracil 


in  a  few  minutes.     The  yields  obtained  by  this  method  of  nitra- 
tion were  very  unifrom  and  are  given  in  the  table  below: 


Nitric  acid, 
sp.  gr.  1.5 

Weight  of 
thymin. 

Weight  of  crude 
oxyni  trohydro- 
thymin. 

Weight  of 
hydropyrimidin 
after  crystalliza- 
tion from  water. 

Percentage  of 
theoretical. 

cc. 

grams. 

grams. 

gram. 

per  cent. 

1 

4 

1.0 

1.1 

0.80 

57.1 

2 

4 

1. 

1.1 

0.82 

58.5 

3 

4 

1. 

1.1 

0.79 

56.4 

4 

4 

1. 

1.1 

0.81 

57.8 

5 

8 

2. 

2.15 

1.60 

55.5 

6 

4 

1. 

1.2 

0.90 

64.4 

7 

8 

2. 

2.1 

1.50 

53.5 

Crystallography  of  Oxynitrohydrothymin  by  W.  E.  Ford. 

The  pyrimidin  crystallizes  in  the  triclinic  system,  showing  a 
combination  of  6  (oio),  c  (ooi),  a  (100),  M  (no),  d  (034)  and  x 
(in).  The  crystals  were  small,  averaging  about  2  mm.  broad 
by  i  mm.  thick.  In  habit  they  present  the  appearance  of  dia- 
mond shaped  tables  with  beveled  edges,  as  is  illustrated  in  the 


figure.  The  face  b  (oio)  is  always  the  most  prominent,  while  the 
prism  with  the  pinacoid  a,  and  the  base  with  the  dome  d  form  the 
beveling  faces.  Frequently  one  of  these  latter  faces  is  much 
subordinated  in  size,  or  may  be  entirely  wanting.  The  negative 
pyramid  x  is  always  small  and  often  not  present.  The  crystal 


Treat  B.  Johnson  413 

faces,  although  distinct  to  the  eye,  were  very  poorly  adapted  for 
measurement  with  the  reflection  goniometer.  They  were  usually 
quite  rough  or  curved  and  gave  indistinct  and  broad  signals  on 
the  goniometer.  A  series  of  the  crystals  were  measured  on  the 
two  circle  goniometer  and  the  average  of  the  best  readings  obtained 
were  taken  for  the  fundamental  angles,  but  the  angles  as  given 
and  the  crystallographic  constants  calculated  from  them  can  be 
considered  only  as  approximate.  The  measured  angles  were  as 
follows : 

(010)  :  (110)  =  63°  54'. 
(010)  :  (100)  =  96°  15'. 
(010)  :  (001)  =  73°  38'. 

Zone  (010). (110)  :  zone  (010). (001)  =  79°  35'. 
Zone  (010). (110)  :  zone  (010). (101)  =  50°  5'. 
(010)  :  (034)  =  71°  33';  calc.  =  71°  46'. 

Using  the  first  five  measurements  as  fundamentals  the  crystal 
constants  were  calculated  to  be: 

a:  b:  c  =  0.578  :  1.000  :  0.420.  a  =  107°  35',  /?  =  100°  25',  r  =  80°  59'. 

The  crystals  show  a  good  cleavage  parallel  to  c  (ooi).  On 
account  of  the  nature  of  the  material  only  a  few  of  the  optical 
facts  concerning  the  compound  could  be  determined.  It  pos- 
sesses a  strong  double  refraction.  The  extinction  direction  on 
b  (oio)  is  inclined  to  the  edge  between  b  and  a  at  31°.  The 
crystals  when  looked  at  in  the  polariscope  in  a  direction  perpen- 
dicular to  c  (ooi),  the  cleavage  face,  show  the  emergence  of  an 
optic  axis  nearly  in  the  center  of  the  field. 

Reduction  of  a-Oxynitrohydrothymin  with  Aluminum- Amalgam. 

Two  and  five-tenths  grams  of  the  hydropyrimidin  were  dis- 
solved in  cold  water  and  reduced  for  1.5  hours  with  an  excess  of 
aluminium-amalgam.  The  temperature  was  not  allowed  to  rise 
above  40°  during  the  reduction.  After  filtering  from  aluminium- 
amalgam  and  aluminium  hydroxide  the  filtrate  was  evaporated 
to  dryness.  I  obtained  a  crystalline  deposit  which  was  difficultly 
soluble  in  cold  water,  but  separated  from  hot  water  in  plates 
melting  at  320°.  When  mixed  with  thymin  the  melting  point 


414  Separation  of  Thymin  from  Uracil 

was  not  lowered.     It  dissolved  in  fuming  nitric  acid  giving  the 
original  a-oxynitrohydrothymin  melting  at  183°  to  185°. 

Calculated  for 

CsHeOaNa:  Found: 

N  ..................................         22.22  22.01 

Reduction  of  a-Oxynitrohydrothymin  with   Tin  and  Hydrochloric 

Acid. 

Two  and  two-tenths  grams  of  the  pyrimidin  were  reduced  for 
one  hour  with  an  excess  of  tin  and  concentrated  hydrochloric 
acid.  The  acid  solution  was  then  evaporated  to  dryness,  the 
residue  dissolved  in  water,  and  the  tin  removed  by  precipitation 
with  hydrogen  sulphide.  When  the  aqueous  nitrate  was  con- 
centrated and  cooled,  thymin  separated  in  glistening  plates 
which  decomposed  at  320°.  Analysis  (Kjeldahl)  : 

Calculated  for 

C5HGO2N2:  Found: 

N  .........................  .........         22.22  22.10 

ft-Oxynitrohydrothymin  : 

NH  —  CO 


CO          C 
I  I        N02 

NH  —  CHOH 

I  have  performed  fifteen  experiments,  during  this  research,  to 
determine  the  behavior  of  fuming  nitric  acid  towards  thymin 
under  different  conditions.  I  have  taken  different  amounts  of 
thymin  (0.5  to  5.0  grams)  and  have  varied  the  proportions  of 
nitric  acid.  I  have  also  allowed  the  acid  solutions  to  evaporate 
under  different  conditions  —  at  room  temperature,  on  the  steam 
oven,  in  a  vacuum  over  sulphuric  acid  and  at  100°  —  but  in  only 
two  experiments  have  I  observed  the  formation  of  /?-oxynitro- 
hydrothymin.  The  conditions,  under  which  I  obtained  this 
isomer  were  as  follows:  One  and  six-tenths  grams  of  thymin 
were  dissolved  in  8  cc.  of  cold,  fuming  nitric  acid  (1.5)  and  the 
solution  allowed  to  evaporate,  in  the  air,  over  night.  The  next 
morning  large,  transparent  blocks  had  deposited  which  showed 
no  signs  of  melting  at  183°  to  185°  but  decomposed  at  230°  to 


Treat  B.  Johnson  415 

235°  according  to  the  rate  of  heating.  One  of  the  crystals 
selected  for  analysis  weighed  0.2600  gram.  The  isomer  did  not 
revert  to  the  a-derivative  when  crystallized  from  water  or  abso- 
lute alcohol,  but  separated  on  cooling  in  well  developed  prisms 
decomposing  at  230°  to  236°.  In  another  experiment  0.5  gram 
of  thymin  was  dissolved  in  10  cc.  of  fuming  nitric  acid  and  the 
solution  allowed  to  evaporate  over  sulphuric  acid,  in  a  vacuum 
desiccator.  I  obtained  practically  a  quantitative  yield  of  the 
/^-derivative  melting  at  230°  to  235°.  The  compound  did  not 
lose  weight  when  heated  for  one-half  hour  at  90°  to  100°. 
Analyses  (Kjeldahl) : 

Calculated  for  Found : 

C5H7O5N3:  I.  II. 

N 22.22  22.00         22.1 

Reduction  of  fi-Oxynitrohydrothymin  with  Tin  and  Hydrochloric 

Acid. 

This  compound  was  reduced  in  the  same  manner  as  the 
a-derivative.  The  excess  of  tin  was  removed  with  hydrogen 
sulphide  and  the  nitrate  evaporated  to  dryness.  I  obtained  a 
crystalline  residue  which  separated  from  water  in  plates  melting 
at  315°  to  320°.  The  compound  sublimed  when  heated  in  a  test- 
tube  and  when  mixed  with  thymin  the  melting  point  was  not 
lowered.  It  dissolved  in  fuming  nitric  acid  giving  a-oxynitro- 
hydrothymin  melting  at  183°  to  185°.  Analysis  (Kjeldahl) : 

Calculated  for 

C5Hr,O2N2:  Found: 


22.22  22.31 


Rearrangement  of  ft-Oxynitrohydrothymin    into   a-Oxynitrohydro- 

thymin. 

Some  of  the  a-pyrimidin,  melting  at  183°  to  185°,  was  pre- 
served in  a  desiccator  from  May  29,  1907,  until  January  17,  1908. 
It  apparently  underwent  no  change  and  melted  at  181°  to  183° 
with  effervescence.  A  sample  of  the  /?-pyrimidin,  melting  at 
230°  to  235°  was  preserved  from  June  19,  1907,  to  October  7, 1907. 
It  then  decomposed  at  227°  to  235°,  and  a  nitrogen  determi- 
nation (Kjeldahl)  gave  22  per  cent  nitrogen;  calculated  22.22 
per  cent.  This  material  was  not  examined  again  until  January 


4i 6  Separation  of  Thymin  from  Uracil 

1 6,  1908.  It  then  had  completely  rearranged  to  the  a-pyri- 
midin  and  melted  at  183°  to  1 88°  with  effervescence.  A  mixture 
of  this  material  and  pure  a-oxynitrohydrothymin  melted  183° 
to  186°.  Analysis  (Kjeldahl) : 

Calculated  for 

C5H7O5N3:  Found: 

N 22.22  21.9 

Method  of  Analysis. 

The  mixture  of  thymin  and  uracil,  which  is  to  be  analyzed,  is 
dried  at  100°,  then  pulverized  finely,  and  dissolved,  at  ordinary 
temperature  (20°),  in  fuming  nitric  acid.  It  is  essential  for  the 
success  of  this  separation  that  the  nitric  acid  have  a  density  of 
1.5  and  that  enough  be  taken  to  react  with  all  the  uracil  and 
thymin  present.  It  has  been  my  experience  that  the  best  pro- 
portions are  about  10  cc.  of  fuming  nitric  acid  for  i  gram  of  the 
pyrimidin  mixture.  The  operation  is  performed  best  in  a 
glass,  crystallizing  dish  of  about  5.5  cm.  diameter,  when  working 
with  i  gram  portions. 

When  the  pyrimidins  have  completely  dissolved  the  solution 
is  evaporated  to  complete  dryness  at  a  temperature  of  50°  to 
60°.  If  impurities  are  present,  which  are  oxidized  by  nitric  acid 
at  this  temperature,  the  excess  of  acid  can  be  removed  by  drying 
in  a  vacuum  over  sulphuric  acid  and  potash.  The  mixture  of 
nitrouracil  and  oxynitrohydrothymin  is  then  pulverized  in  a 
mortar  and  triturated  thoroughly  with  cold,  absolute  alcohol, 
using  15  cc.  of  alcohol  for  each  gram  of  the  original  mixture. 
The  insoluble  nitrouracil  is  filtered  off  with  suction,  washed  with 
5  cc.  of  cold  alcohol  and  purified  by  recrystallization  from  hot 
alcohol  or  water.  It  is  identified  in  the  manner  described  above. 

In  order  to  obtain  the  oxynitrohydrothymin  the  alcohol  wash- 
ings are  allowed  to  evaporate  spontaneously  in  a  good  draught. 
It  is  not  advisable  to  remove  the  alcohol  by  heating  on  the 
steam  bath.  After  removal  of  the  alcohol  the  oxynitrodrothy- 
min  is  recrystallized  from  the  least  possible  quantity  of  hot  water 
and  identified  by  its  characteristic  melting  point  and  crystalline 
habit. 

The  results  of  the  analyses  of  three  different  mixtures  of  uracil 
and  thymin  are  given  in  the  following  table: 


Treat  B.  Johnson 


417 


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CO      N             ON 

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418  Separation  of  Thymin  from  Uracil 

I  take  pleasure  in  thanking  Professor  Ford  for  the  crystallo- 
graphic  description  of  oxynitrohydrothymin. 


Reprinted  from  the  American  Chemical  Journal.    Vol.  XI,.    No.  i. 

July,  1908.] 
[Contributions  from  the  Sheffield  Laborotory  of  Yale  University.] 

CLVI.  RESEARCHES  ON  PYRIMIDINES.     THE  ACTION 

OF  NITRIC  ACID  ON  2,6-DIOXYPYRIMIDINES. 

OXYNITROHYDROTHYMINE. 

[THIRTIETH  PAPER.] 

BY  TREAT  B.  JOHNSON. 

I  shall  describe,  in  this  paper,  some  results  which  I  have  ob- 
tained by  examining  the  behavior  of  fuming  nitric  acid  towards 
5-bromuracil,  5-chloruracil,  and  synthetical  thymine. 

In  a  paper  entitled  "Die  Constitution  des  Thymins,"1  Steudel 
has  described  the  action  of  concentrated  nitric  acid  on  thymine. 
He  obtained  a  compound  to  which  he  assigned  the  empirical 
formula  C4H4O3N4.  He  gave  no  melting  point  for  the  com- 
pound, but  states  that  it  did  not  contain  water  of  crystallization, 
that  it  was  soluble  in  warm  water  and  ammonia,  and  gave,  on 
reduction,  a  derivative  which  responded  to  Weidel's  alloxan 
reaction.  I  have  repeated  Steudel' s  experiment  and  have 
investigated  the  action  of  nitric  acid  of  different  concentrations 
and  under  various  conditions,  but  in  no  case  have  I  obtained  a 
compound  identical  with  his  nitrothymine.  The  data  which  I 
have  obtained  seem  to  indicate  that  Steudel's  nitrothymine  was 
a  secondary  decomposition  product,  and  not  a  simple  thymine 
derivative. 

Uracil,  5-bromuracil,  5-chloruracil,  and  thymine  do  not  react, 
below  100°,  with  nitric  acid  of  density  i  .41 .  On  the  other  hand, 
uracil  dissolves,  at  ordinary  temperature,  in  fuming  nitric  acid 
(sp.  gr.  1.5),  giving  a  good  yield  of  5-nitrouracil  (I.).  5-Brom- 
uracil,  5-chloruracil,  and  thymine  react,  under  the  same  con- 
ditions, giving  three  derivatives  corresponding  to  the  empirical 
formulas  II.,  III.,  and  IV.,  respectively.  The  same  compound 
IV.  was  also  obtained  when  thymine  was  treated  with  concen- 
trated nitric  acid  according  to  the  directions  of  Steudel.2 

Uracil,  C4H402N2          ->  C4H3O2N2(NO2),  I.    (5-Nitro- 

uracil). 

5-Bromuracil,  C4H3O2N2(Br)  ->  C4H3O2N2(Br)HNO3,  II. 
5-Chloruracil,  C4H3O2N2(C1)  -^  C4H3O2N2(C1)HNO3,  III. 
Thymine,  C4H3O2N2(CH3)->  C4H3O2N2(CH3)HNO3,  IV. 

1  Z.  physiol.  Chem.,  32,  241. 

2  Loc.  tit. 


20  Johnson. 

I  now  find  that  the  compound  II.,  prepared  from  5-bromuracil 
and  nitric  acid,  is  identical  with  bromnitrooxyhydrouracil,  V., 
which  Behrend1  obtained  by  treatment  of  nitrouracil  with 
bromine  water.  This  interesting  result,  and  the  fact  that  the 
analogous  compounds,  III.  and  IV.,  are  prepared  under  the 
same  conditions,  indicate  that  they  have  a  similar  structure 
and  are  to  be  considered  as  oxynitrohydropyrimidines ;  viz., 
chlornitrooxyhydrouracil,  VI.,  and  oxynitrohydrothymine, 
VII.,  respectively: 

NH CO  NH CO  NH CO 

I  I  /Br  |  |  /Cl  |  A 

CO          C<         ,  CO         C<          ,  CO          C< 

I  I  XNO2  |  |  XN02  |  |    \N02 

NN CHOH  NH CHOH  NH CHOH 

V.  VI.  VII. 

The  formation  of  these  hydropyrimidines  involves  a  direct 
addition  of  nitric  acid  to  the  double  bond  between  the  4  and  5 
positions  of  the  pyrimidine  ring.  The  preparation  of  brom- 
nitrooxyhydrouracil, V.,  from  5-nitrouracil  and  5-bromuracil 
shows  that  the  nitro  group  and  bromine  atom  are  linked  to  the 
same  carbon  atom.  It  also  proves  Behrend' s2  original  con- 
clusion that  the  formation  of  oxyhydropyrimidines,  from  cer- 
tain pyrimidines,  by  the  action  of  chlorine  and  bromine  water 
involves  an  addition  of  hypochlorous  and  hypobromous  acids 
at  the  double  bond. 

NH CO  NH CO  NH CO 

CO        CBr  +  HN03  ->  CO        C  /        <-  H2O  +  Br2  +  CO        CNO 
|  II  II  XN02  |  || 

NH CH  NH CHOH  NH CH 

v. 


I 


NH  -  CO  NH  --  CO 

I  I  /Br  |  |  /NO, 

CO        C<  CO        C< 

I  I    X>H  |  |  XOH 

NH  --  CHNO2  NH  --  CHBr 

VIII.  IX. 

1  Ann.  Chem.  (Liebig),  240,  11. 

2  Ann.  Chem.  (Liebig),  229,  20. 


Researches  on  Pyrimidines.  21 

I  also  find  that  5-bromuracil  and  5-chloruracil  react  with 
chlorine  water  and  bromine  water,  respectively,  giving  the  same 
chlorbromoxyhydrouracil,  X.  When  this  hydropyrimidine 
was  digested  with  alcohol  it  was  converted  into  5-chloruracil. 

NH CO  NH CO  NH— CO 

I  I  I  /Cl  || 
CO        CBr  +  H2O  +  Cl,  ->  CO        C<       T>  Br,  -f  H2O  +  CO       CC 

II  I  I  XBr  |  || 
NH CH                                 NH CHOH                                 NH— CE 

X. 

Thymine  apparently  shows  no  tendency  to  form  salts  with 
acids.  It  can  be  crystallized  from  concentrated  hydriodic  and 
hydrobromic  acids  without  alteration.  The  possibility  of  the 
nitro  derivative  IV.  being  a  nitric  acid  salt,  XI.  is  excluded 
since  thymine  is  not  formed  by  treatment  with  alkalis,  and  also 
because  it  does  not  react  with  bromine  water  to  give  oxybrom- 
hydro  thy  mine. 1  The  compound  is  not  a  substituted  nitro 
derivative,  as  represented  by  formulas  XII.,  XIII.,  and  XIV., 
because  it  does  not  contain  water  of  crystallization.  It  can  be 
crystallized  repeatedly  from  absolute  alcohol  without  alteration. 

NH CO  N02N CO  NH— CO 

II  II  II 

CO        CCH3.HN03       CO       CCH3.H20        CO      CCH3.H2O 

I             II                             I           II                         I  II 

NH CH  NH— CH  NO2N CH 

XI.  XII.  XIII. 

NH CO 

I  I 

CO        CCH2N02.H20. 

I  II 

NH CH 

XIV. 

I  have  made  the  interesting  observation  that  oxynitrohy- 
drothymine,  VII.,  can  exist  in  two  modifications  which  I  have 
designated  by  the  Greek  letters  a  and  ft.  The  two  isomers  are 
obtained  under  practically  the  same  conditions.  The  a.  deriva- 
tive is  the  stable  modification  and  melts  at  i83°-i85°.  The 
ft  derivative  melts  at  23o°-235°  and  rearranges  to  the  a  form  at 

1  Jones:     Z.  physiol.  Chem.,  29,  20. 


22  Johnson. 

ordinary  temperature.  The  two  isomers  are  especially  char- 
acterized by  their  crystalline  habit  and  are  converted  quantita- 
tively into  thymine  when  reduced  with  tin  and  hydrochloric 
acid.  This  interesting  case  of  isomerism  is  possibly  similar  in 
nature  to  that  recently  observed  by  Osten.1  He  found,  for 
example,  that  methylisodialuric  acid,  XV.,  and  its  diethyl  ether, 
XVI.,  occur  in  two  isomeric  modifications  which  undergo  re- 
versible transformations  in  the  presence  of  acids  and  alkalis. 

NH  -  CO  NH  -  CO 

I  I  /OH  |   /OC,H5 

CO          C<  CO          C< 

I  I  XOH  |  |    X)C2H5 

NH  -  COH  NH  -  COH 

CHS  CH3 

XV.  XVI. 

Oxynitrohydropyrimidines  are  probably  formed  in  every  case 
when  5-nitropyrimidines  are  obtained  by  the  action  of  nitric 
acid.  For  example:  the  formation  of  nitrouracil  from  uracil 
probably  involves  an  addition  of  nitric  acid,  giving  the  unstable 
hydropyrimidine  XVII.,  which  then  breaks  down  with  loss  of  a 
molecule  of  water,  giving  nitrouracil.  In  the  case  of  thymine, 
on  the  other  hand,  the  molecule  cannot  lose  water  in  the  normal 
manner  and  therefore  the  intermediate  hydropyrimidine,  VII., 
is  capable  of  isolation. 

NH—  CO  NH—  CO  NH—  CO 


CO    CH  +  HNO3—  CO    C<       ->  CO    CNO2-fH2O. 

H          |        || 
NH—  CH  NH—  CHOH        NH—  CH 

XVII. 

It  is  interesting  to  note  here  the  behavior  of  nitric  acid  to- 
wards hydrouracil.2  This  compound  contains  no  double  bond 
between  the  4  and  5  positions  and  the  5  position  is  not  the  point 
of  attack.  It  reacts  with  nitric  acid,  giving  a  nitro  derivative, 
XVIII.,  in  which  the  nitro  group  is  linked  to  the  3  position  of 
the  pyrimidine  ring. 

1  Ann.  Chem.  (Liebig),  343,  133. 

2  Franchimont  and  Friedmann:  Rec.  trav.  chim.,  26,  218. 


Researches  on  Pyrimidines. 


NH CO  NH- 

I  I  I 

CO          CH2  +  HNO3  F*         CO 


NH CH, 


NO2N- 


XVIII. 


-CO 

CH2  +  H2O. 
•CH, 


The  isolation  of  the  above  oxynitrohydropyrimidines  lends 
new  interest  to  some  early  observations  on  the  action  of  nitric 
acid  on  certain  benzene  derivatives.  For  example:  nitric  acid 
reacts  with  toluene,  in  presence  of  sulphuric  acid,  giving  3, 
5-dinitroparacresol,  XIX.,  and  3,5-dinitroorthocresol,  XX.1 
Orthoxylene  gives  a  mixture  of  3,5-dinitroparaxylenol,  XXI., 
and  3,5-dinitroorthoxylenol,2  XXII.  Orthocresolsulphonic 
acid  reacts  with  nitric  acid,  giving  3,5-dinitroorthocresol,8  XX. 
Similar  observations  have  also  been  made  in  the  naphthalene 
series.4  Armstrong  explains  these  abnormal  reactions  by  as- 
suming an  addition  of  nitric  acid  to  a  double  bond  in  the  benzene 
ring,  giving  unstable  addition  products.  These  then  break 
down  in  two  ways,  either  with  separation  of  nitrous  acid,  giving 
a  phenol,  or  with  loss  of  water,  giving  a  nitro  derivative.  ' ;': 

CHS 
\ 


NO. 


NO2 


N02         NO2 


OH 
XIX. 


\/ 

XX. 

CH3 


OH 
N02 


\ 


NO2 


XXII. 

1  Nolting  and  Forel:  Ber.  d.  chetn.  Ges.,  18,  2670. 

2  Nolting  and  Pick:  Ibid.,  21,  3158. 

3  Claus  and  Jackson:  J.  prakt.  Chem.  (2),  38,  333. 

4  Armstong  and  Rossiter:  P.  Chem.  Soc.,  1891,  87-89;  Ber.  d.  chera.  Ges.,  24, 
R.  721. 


Johnson. 


The  action  of  nitric  acid  on  orthocresolsulphonic  acid, 
XXIII.,  may  be  represented  by  the  following  equation.  The 
writer  is  not  aware  that  such  intermediate  addition  products 
with  nitric  acid  have  been  isolated  in  the  benzene  series. 


CH3 


CH, 


\S03H 


H2  O  -f  H2S04. 


EXPERIMENTAL   PART. 

The  Action  of  Nitric  Acid  (sp.  gr.  1.5)  on  s-Bromuracil. 

NH CO 

1  l/Br 

Oxynitrobromhydrouracil,  CO          C<(          . — This  compound 

|\N02 

NH CHOH 

was  first  described  by  Behrend.1  I  prepared  it  in  the  following 
manner:  Three  grams  of  finely  pulverized  5-bromuracil  were 
dissolved  in  19  cc.  of  nitric  acid  and  the  solution  allowed  to 
evaporate  in  a  vacuum  over  sulphuric  acid.  I  obtained  3.3 
grams  of  the  pure  hydropyrimidine  which  crystallized  in  large 
blocks  and  rectangular  prisms.  The  pyrimidine  had  no  definite 
melting  point,  but  decomposed  from  150°  to  165  °  according  to  the 
rate  of  heating.  It  was  difficultly  soluble  in  cold  water  but 
could  not  be  purified  by  recrystallization  from  this  solvent. 
When  warmed  with  water  above  40°  it  was  decomposed  with 

1  Loc.  ctt. 


Researches  on  Pyrimidines.  25 

formation  of  brompicrin,  which  was  recognized  by  its  disa- 
greeable odor.  The  pyrimidine  did  not  contain  water  of  crystal- 
lization. It  agreed  in  its  chemical  behavior,  so  far  as  I  was  able 
to  judge,  with  the  hydropyrimidine  described  by  Behrend. 

0.3006  gram  of  substance  gave  0.2204  gram  CO2  and  0.0481 
gram  H2O.     Nitrogen  (Kjeldahl). 

Calculated  for  Found. 

C4H405N8Br.  I.  II. 

C  IQ.OO  20.00 

H  1.57  1.77 

N  16.53  •••  16.35 

ReductionofOxynitrobromhydrouracilwithTin  and  Hydrochloric 
Acid. — Two  grams  of  the  hydropyrimidine  were  reduced,  on  the 
steam  bath,  for  one  hour  with  an  excess  of  tin  and  hydrochloric 
acid.  The  solution  was  then  evaporated  to  dryness  to  remove 
the  excess  of  hydrochloric  acid  and  the  residue  redissolved  in 
water.  The  tin  was  then  removed  by  precipitation  with  hy- 
drogen sulphide  and  the  filtrate  concentrated  to  a  volume  of  20 
cc.  Five  grams  of  potassium  cyanate  were  then  added  to  the 
solution  when  I  obtained  an  insoluble,  granular  precipitate. 
The  compound  was  difficultly  soluble  in  hot  water  and  prac- 
tically insoluble  in  the  common  organic  solvents  and  dilute 
sulphuric  acid.  It  did  not  contain  halogens,  and  left  no  in- 
organic residue  when  burned  on  a  platinum  foil.  When  the 
compound  was  warmed  with  bromine  water  and  then  treated 
with  an  excess  of  barium  hydroxide  solution,  a  purple  precipitate 
was  obtained.  Its  characteristic  properties  and  nitrogen 
determinations  identified  the  compound  as  Behrend's1  hy- 
NH CO 

I  I 

droxyxanthine,   CO          CNHCONH2. 

I  II 

NH CH 

Nitrogen  (Kjeldahl) : 

Calculated  for  Found. 

C5H6O3N4.  I.  II. 

N  32.94  32-8o  32.95 

1  Ann.  Chem.  (Liebig),  229,  40;  240,  6. 


26  Johnson. 

NH CO 

Oxydichlorhydrouracil,  CO  C  <^      .  H2O. — This  compound 

NH CHOH 

was  prepared  by  dissolving  uracil  in  an  excess  of  strong  chlorine 
water,  or  by  oxidizing  uracil  with  potassium  chlorate  and  dilute 
hydrochloric  acid.  Five  grams  of  finely  pulverized  uracil  were 
suspended  in  about  100  cc.  of  chlorine  water  and  chlorine  gas 
conducted  into  the  solution  until  the  pyrimidine  had  dissolved. 
The  excess  of  chlorine  was  then  removed  with  a  current  of  air 
and  the  solution  concentrated  on  the  steam  bath.  On  cooling, 
prismatic  crystals  of  chloruracil  (see  below)  deposited.  These 
were  removed  by  filtration  and  the  filtrate  concentrated  further. 
The  hydropyrimidine  then  separated,  on  cooling,  in  the  form  of 
tables  melting  at  205^-208°  with  effervescence.  In  a  second 
experiment  2  grams  of  uracil  were  dissolved  in  80  cc.  of  20  per 
cent  hydrochloric  acid  and  the  solution  heated  to  7o°-9O°. 
Potassium  chlorate  was  then  occasionally  added  in  small  portions 
and  the  oxidation  continued  at  5o°-6o°  for  four  hours.  The 
excess  of  chlorine  was  then  removed  in  the  usual  manner  and 
the  solution  allowed  to  stand.  The  oxydichlorhydrouracil 
finally  separated  in  stout  prisms  which  decomposed  at  208°- 
210°.  The  hydropyrimidine  crystallized  from  water  in  large, 
well- developed  prisms  melting  at  2i2°-2i5°  with  effervescence. 
Aqueous  solutions  of  the  pyrimidine  gave  a  purple  precipitate 
when  warmed  with  a  solution  of  barium  hydroxide.  The 
pyrimidine  was  recovered  unaltered  after  boiling  with  alcohol 
for  24  hours.  The  corresponding  dibrom  derivative1  is  con- 
verted into  5-bromuracil  by  the  same  treatment.  Oxydichlor- 
hydrouracil contained  one  molecule  of  water  of  crystallization 
which  was  determined  by  heating  for  one  hour  at  ioo°-no°. 
0.9157  gram  of  substance  lost  0.0778  gram  of  H2O. 

Calculated  for 
C^^sNaClg-HjO.  Found. 

H2O  8.30  8.49 

Nitrogen  determination  for  hydrous  pyrimidine  (Kjeldahl) : 

Calculated  for 

aO.  Found. 


N  12.90  12.67 

i  Wheeler  and  Johnson:  J.  Biol.  Chem.,  3,  183. 


Researches  on  Pyrimidines.  27 

NH CO 

5-Chloruracil,  CO  CC1- — This  compound  was  always  ob- 

!  I! 

NH CH 

tained  associated  with  oxydichlorhydrouracil  when  uracil  was 
treated  with  chlorine  water.  It  can  be  prepared  by  reducing 
the  hydropyrimidine  with  tin  and  hydrochloric  acid.  The  pyrimi- 
dine  separated  from  the  acid  solution  in  the  form  of  rectangular 
prisms  and  square  tables.  It  was  practically  insoluble  in  alco- 
hol and  cold  water.  It  crystallized  from  hot  water  in  prisms 
melting  at  3oo°-3O5°  according  to  the  rate  of  heating.  The 
pyrimidine  did  not  contain  water  of  crystallization.  Nitro- 
gen (Kjeldahl) : 

Calculated  for  Found. 

C4H302N2C1.  I.  II.  III. 

N                  19.11             19.03         19.5         19.00 
NH CO 

I    /Cl 
Oxynitrochlorhydrouracil,    CO          C(  .  iJH2O.  —  This 

I  XN02 

NH CHOH 

pyrimidine  was  prepared  by  dissolving  i .  o  gram  of  5-chlor- 
uracil  in  10  cc.  of  fuming  nitric  acid  (sp.  gr.  1.5).  When  the 
solution  was  allowed  to  evaporate  spontaneously,  in  the  at- 
mosphere, the  pyrimidine  separated  in  hard,  prismatic  crys- 
tals. The  substance  had  no  definite  melting  point  but  de- 
composed with  effervescence  from  150°  to  160°,  according  to 
the  rate  of  heating.  It  slowly  underwent  decomposition 
when  heated  at  ioo°-iio°  and  was  also  decomposed  by  boil- 
ing water.  The  compound  contained  water  of  crystalliza- 
tion (Analysis  I.),  which  it  slowly  lost  when  exposed  to  the 
atmosphere.  After  drying  over  sulphuric  acid,  in  a  desicca- 
tor, for  6  days,  the  analytical  determination  agreed  with  the 
calculated  value  for  the  anhydrous  material  (Analyses  II. 
and  III.).  (Kjeldahl): 

Calculated  for  Found. 

C4H405N3Cl.iiHjO.  I. 

•N  17.75  17-7 

Calculated  for  Found. 

C4H406N3C1.  II.  III. 

N  20.04  J9-57         19-6 


28  Johnson. 

NH CO 

I  I   /Cl 

Oxychlorbromhydrouracil,    CO          C<(       .H2O. — This   pyr- 

I  |XBr 

NH CHOH 

imidine  can  be  prepared  from  5-bromuracil  or  5-chloruracil 
by  dissolving  them  in  an  excess  of  chlorine  water 
and  bromine  water,  respectively.  It  was  very  soluble  in 
water  and  crystallized  from  bromine  water  in  prismatic  crys- 
tals, decomposing  at  i95°-2oo°,  with  effervescence.  It  re- 
acted with  barium  hydroxide,  in  aqueous  solution,  giving  a 
purple  precipitate.  The  pyrimidine  contained  one  molecule 
of  water  of  crystallization,  which  was  determined  by  heating 
for  one  hour  at  9o°-no°.  The  compound  slowly  loses  its 
water  of  crystallization  in  the  atmosphere  and  becomes  anhy- 
drous after  standing  for  several  hours  in  a  desiccator  over 
sulphuric  acid. 

I.  0.7413  gram  substance  lost  0.0516  gram  H2O. 
II.  0.2029  gram  substance  lost  0.0123  gram  H2O. 

Calculated  for  Found. 

C4H4O3N»ClBr.H2O.  I.  II. 

H2O  6.88  6.95  6.50 

Nitrogen  determination  for  hydrous  pyrimidine  (Kjeldahl) : 

Calculated  for 
C4H4O3N2ClBr.H,O.  Fo  v.nd. 

N  10.70  10.66 

Nitrogen  determination  for  anhydrous  pyrimidine  (Kjel- 
dahl) : 

Calculated  for  Found. 

C4H4O8N2ClBr.  I.  II. 

N  n-49  11.31  ii.  4 

Action  of  Boiling  Alcohol  on  Oxychlorbromhydrouracil. — 
Five-tenths  of  a  gram  of  the  hydropyrimidine,  melting  at 
i95°-2oo°,  was  dissolved  in  20  cc.  of  absolute  alcohol  and 
the  solution  boiled  for  ten  hours.  The  alcohol  was  then  re- 
moved by  evaporation  and  the  product  obtained  was  crys- 
tallized from  hot  water.  It  separated  in  stout  prisms,  decom- 
posing at  3OO°-305°.  It  gave  a  test  for  chlorine  and  a  mix- 


Researches  on  Pyrimidines.  29 

ture  of  the  compound  and  5-chloruracil  decomposed  sharply 
at  300°-305°.     Analysis  (Kjeldahl)  : 

Calculated  for  Calculated  for 

C4H3O7N2C1.  C4H3O2N2Br.  Found. 

N  19.11  14.66  19-04 

Action  of  Bromine  Water  on  j-Iodouracil.  —  5-Iodouracil  was 
decomposed  by  bromine  water  with  liberation  of  iodine.  About 
i  gram  of  the  pyrimidine  was  dissolved  in  bromine  water,  and 
the  solution  allowed  to  evaporate  spontaneously  in  the  atmos- 
phere. Transparent  prisms  finally  separated,  which  decom- 
posed sharply  at  2oo°-205°.  The  compound  did  not  con- 
tain iodine,  but  gave  a  strong  test  for  bromine.  It  was  con- 
verted into  5-bromuracil  when  heated  with  absolute  alcohol. 
A  nitrogen  determination  agreed  with  the  calculated  value 
for  oxydibromhydrouracil1  (Kjeldahl)  : 

Calculated  for 

C4H4O3N2Br2.  Found. 

N  9.72  9.6 

The  Action  of  Nitric  Acid  on  Thy  mine. 

Nitric  Acid  (sp.  gr.  1.415).  —  Five-  tenths  of  a  gram  of  thy- 
mine  was  dissolved  in  2  cc.  of  concentrated  nitric  acid  and 
the  solution  evaporated  to  dry  ness  on  the  steam  bath.  There 
was  no  evidence  of  any  reaction  and  the  thymine  was  recov- 
ered unaltered.  It  deposited  from  hot  water  in  plates  that 
decomposed  at  about  321°.  When  mixed  with  pure  thymine 
this  decomposition  point  was  not  lowered. 

Analysis  (Kjeldahl)  : 

Calculated  for 

Found. 


N  22.22  22.23 

Nitric  Acid  (sp.  gr.  J-5).     The  Formation  of  a-Oxynitrohy- 
NH  -  CO 

I  I    /CHS 

drothymine,    CO          C^         •  —  Thymine    dissolves    in    cold, 

I  I  XNO, 

NH  -  CHOH 

fuming  nitric  acid  with  slight  evolution  of  heat.     If  red  fumes 
are  evolved  by  this  treatment  it  is  a  safe  indication  that  the 

1  Wheeler  and  Johnson:  Loc.  cit. 


30  Johnson. 

thy  mine  is  not  pure.  The  hydropyrimidine  was  obtained 
perfectly  pure,  and  the  yield  was  quantitative,  when  thy- 
mine  was  treated  with  fuming  nitric  acid  under  the  following 
conditions:  One  gram  of  thy  mine  was  dissolved  in  6  cc. 
of  nitric  acid  and  the  solution  allowed  to  evaporate  at  ordi- 
nary temperature.  The  nitro  derivative  deposited  in  large, 
well-developed  prisms  or  blocks,  which  decrepitated  above 
130°  and  melted  at  183°  with  violent  effervescence.  The 
compound  was  soluble  in  hot  water,  extremely  soluble  in  alco- 
hol, and  separated  from  both  these  solvents  in  blocks  that 
melted  at  i83°-i85°.  It  was  practically  insoluble  in  ben- 
zene. The  pyrimidine  did  not  lose  weight  after  heating  for 
1.5  hours  at  ioo°-no°  and  again  for  one-half  hour  at  no°- 
115°.  When  heated  above  120°  it  slowly  underwent  decom- 
position. The  composition  of  the  compound  was  not  altered 
by  recrystallization  from  absolute  alcohol  (Analysis  III.). 

0.2086  gram  substance  gave  0.2454  gram  CO2  and  0.0695 
gram  H2O. 

Nitrogen  (Kjeldahl) : 

Calculated  for      Calculated  for  Found. 

C6H7O5N3.  C6H6O2N2.  I.  II.  III. 

C  31-74  47-6i          32.08      I  ... 

3.70  4.76  3.70 

N  22.22  22.22  ...  22. OO       21. 95 

a-Oxynitrohydrothymine  dissolves  in  water,  giving  an 
acid  reaction.  The  pyrimidine  undergoes  decomposition  when 
its  aqueous  solution  is  boiled.  The  addition  of  barium  hy- 
droxide to  its  aqueous  solution  produces  no  precipitate  or 
color;  also  no  thymine  deposited  when  an  alcoholic  solution 
of  the  pyrimidine  was  treated  with  ammonia.  When  the 
nitropyrimidine  was  dissolved  in  concentrated  sulphuric 
acid,  and  a  few  drops  of  ferrous  sulphate  solution  were  added, 
the  characteristic  test  for  nitric  acid  was  obtained.  a-Oxy- 
nitrohydrothymine  can  also  be  prepared  by  dissolving  thy- 
mine in  fuming  nitric  acid  (sp.  gr.  i .  5)  and  evaporating  the 
solution  to  dryness,  at  once,  on  the  steam  bath.  This  method 
of  nitration  can  be  recommended  for  preparing  quickly  small 
quantities  of  the  hydropyrimidine.  The  yields  are  not  quan- 


Researches  on  Pyrimidines.  31 

titative,  since  part  of  the  thymine  undergoes  oxidation.  The 
best  results  are  obtained  when  i  gram  portions  are  nitrated 
under  the  following  conditions:  One  gram  of  thymine  is 
dissolved  in  4  cc.  of  nitric  acid  (sp.  gr.  1.5)  and  the  solution 
evaporated  to  dry  ness  as  quickly  as  possible.  The  nitrothy- 
mine  is  obtained  as  a  colorless,  crystalline  residue  which 
separates  from  water  in  blocks  decomposing  at  i83°-i85°< 
It  is  possible,  in  this  manner,  to  prepare  several  grams  of  the 
hydropyrimidine  in  a  few  minutes.  The  yields  obtained  by 
this  method  of  nitration  were  very  uniform  and  are  given  in 
the  table  below. 

«  5* 

O.  *-  S  uT3  E  >>">««« 

*  rt  v  >>o  «"  JJ  -2  **  0 

D  *  »C   jj 

~  bo  B 

*•*    >O  "*^  *S 

•*ti  M  6 

&       &         P 

1  4  i 

2  4  i 

3  4  i 

4  4  i 

5  8  2' 
641 

7  8  2 

Crystallography  of  Oxynitrohydrothymine. 

By  W.  E.  FORD. 

The  pyrimidine  crystallizes  in  the  triclinic  system,  show- 
ing a  combination  of  b  (oio),  c  (ooi),  a  (100),  M  (no),  d  (034) 
and  X  (in).  The  crystals  were  small,  averaging  about  2 
mm.  broad  by  i  mm.  thick.  In  habit  they  present  the  appear- 
ance of  diamond- shaped  tables  with  beveled  edges,  as  is  illus- 
trated in  the  figure.  The  face,  b  (oio),  is  always  the  most 
prominent,  while  the  prism  with  the  pinacoid,  a,  and  the  base 
with  the  dome,  d,  form  the  beveling  faces.  Frequently  one 
of  these  latter  faces  is  much  subordinated  in  size,  or  may  be 
entirely  wanting.  The  negative  pyramid,  X,  is  always  small, 
and  often  not  present.  The  crystal  faces,  although  distinct 
to  the  eye,  were  very  poorly  adapted  for  measurement  with 


bfi 

gf 

fEft 

I® 

£ 

P 

I 

.  I 

0.80 

57-i 

I 

.  I 

0.82 

58.5 

I 

.  I 

0.79 

56.4 

I 

.  I 

0.81 

57-8 

2 

•15 

i.  60 

55-5 

I 

.2 

0.90 

64.4 

2 

.1 

1.50 

53-5 

Johnson. 


the  reflection  goniometer.  They  were  usually  quite  rough  or 
curved  and  gave  indistinct  and  broad  signals  on  the  goniom- 
eter. A  series  of  the  crystals  was  measured  on  the  two- 
circle  goniometer,  and  the  average  of  the  best  readings  ob- 


tained was  taken  for  the  fundamental  angles,  but  the  angles 
as  given  and  the  crystallographic  constants  calculated  from 
them  can  be  considered  only  as  proximate.  The  measured 
angles  were  as  follows : 


(oio)  :  (no)  =  63°54'. 
(oio)  :  (100)  =  96°i5'- 
(oio)  :  (ooi)  =  73°38'- 
Zone  (oio)  .  (no)  :  Zone  (oio) 
Zone  (oio)  .  (no)  :  Zone  (oio) 


(ooi) 
(101) 


79°35'. 
5o°5'. 


(oio)  :  (034)  =  7i°33';  calc.  =  7i°46'- 

Using  the  first  five  measurements  as  fundamentals,  the 
crystal  constants  were  calculated  to  be 

a:b:c  =  0.578:1.000:0.420.       a  =   io7°35',  /?  —   looks', 

T  =  8o°59'. 

The  crystals  show  a  good  cleavage  parallel  to  c  (ooi).  On 
account  of  the  nature  of  the  material  only  a  few  of  the  optical 
facts  concerning  the  compound  could  be  determined.  It 
possesses  a  strong  double  refraction.  The  extinction  direc- 
tion on  6  (oio)  is  inclined  to  the  edge  between  b  and  a  at  31°. 
The  crystals,  when  looked  at  in  the  polariscope  in  a  direction 


Researches  on  Pyrimidines.  33 

perpendicular  to  c  (ooi),  the  cleavage  face,  show  the  emer- 
gence of  an  optic  axis  nearly  in  the  center  of  the  field. 

Action  of  Nitric  Acid  (sp.  gr.  1.5)  in  Presence  of  Concentra- 
ted Sulphuric  Acid. — There  was  an  immediate  reaction,  with 
evolution  of  red  fumes,  when  o .  5  gram  of  thymine  was  dis- 
solved in  a  mixture  of  3  cc.  of  nitric  and  3  cc.  of  sulphuric 
acids.  When  the  mixture  was  allowed  to  stand,  without 
cooling,  the  reaction  continued  to  increase  in  violence,  with 
evolution  of  heat,  and  the  thymine  was  completely  decom- 
posed. In  a  second  experiment,  i  gram  of  thymine  was  dis- 
solved in  a  cold  mixture  of  3  cc.  nitric  and  2  cc.  concentrated 
sulphuric  acids.  This  solution  was  held  at  a  temperature 
of  7o°-75°  for  about  three-quarters  of  an  hour,  when  gas  bub- 
bles had  practically  ceased  to  be  formed.  The  acid  solution 
was  then  cooled  and  poured  into  15  cc.  of  ice  water.  After 
standing  for  several  hours,  stout,  well-developed  prisms  de- 
posited from  the  solution.  They  melted  at  i83°-i85°,  with 
effervescence,  and  were  identified  as  oxynitrohydrothymine. 
They  were  soluble  in  alcohol  and  warm  water.  Analysis 
(Kjeldahl) : 

Calculated  for 

C5H7O6N3.  Found. 

N  22.22  21.66 

Action  of  Bromine  Water  on  a-Oxynitrohydrothymine. — One 
gram  of  the  hydropyrimidine  was  dissolved  in  an  excess  of 
bromine  water  and  the  solution  allowed  to  evaporate  spon- 
taneously. There  was  no  evidence  of  a  reaction  and  oxy- 
nitrohydrothymine separated  in  large,  transparent  blocks 
melting  at  i83°-i85°. 

Analysis  (Kjeldahl) : 

Calculated  for 

C6H7O5N3.  Found. 

N  22.22  22.42 

Reduction  of  a-Oxynitrohydrothymine  with  Aluminum  Amal- 
gam.— Two  and  five- tenths  grams  of  the  hydrothymine  were 
dissolved  in  cold  water  and  reduced  for  1.5  hours  with  an 
excess  of  aluminum  amalgam.  The  temperature  was  not 
allowed  to  rise  above  40°  during  the  reduction.  After  fil- 


34  Johnson. 

tering  from  aluminum  amalgam  and  aluminum  hydroxide 
the  filtrate  was  evaporated  to  dryness.  I  obtained  a  crys- 
talline deposit  which  was  difficultly  soluble  in  cold  water, 
but  separated  from  hot  water  in  plates  melting  at  320°.  When 
mixed  with  thy  mine  the  melting  point  wras  not  lowered.  It 
dissolved  in  fuming  nitric  acid,  giving  the  original  a-oxyni- 
trohydrothymine  melting  at  i83°-i85°.  Analysis  (Kjeldahl) : 

Calculated  for 

C6H6OeN2.  Found. 

N  22.22  22.01 

Reduction  of  a-Oxynitrohydrothymine  with  Tin  and  Hydro- 
chloric Acid. — Two  and  two- tenths  grams  of  the  hydropyrimi- 
dine  were  reduced  for  one  hour  with  an  excess  of  tin  and  con- 
centrated hydrochloric  acid.  The  acid  solution  was  then  evapo- 
rated to  dryness,  the  residue  dissolved  in  water,  and  the  tin 
removed  by  precipitation  with  hydrogen  sulphide.  When 
the  aqueous  filtrate  was  concentrated  and  cooled,  thy  mine 
separated  in  glistening  plates,  decomposing  at  320°.  Analy- 
sis (Kjeldahl) : 

Calculated  for 

C5H6O2Na.  Found. 

N                                               22.22  22.10 

HH CO 

I  I    /CH3 

ft-Oxynitrohydrothymine,    CO  C  <^         •  —  I   have   per- 

I  I  XN02 

NH CHOH 

formed  fifteen  experiments,  during  this  research,  to  determine 
the  behavior  of  fuming  nitric  acid  towards  thymine  under 
different  conditions.  I  have  taken  different  amounts  of 
thymine  (o .  5—5 .  o  grams) ,  and  have  varied  the  proportions 
of  nitric  acid.  I  have  also  allowed  the  acid  solution  to  evapo- 
rate under  different  conditions — at  room  temperature,  on 
the  steam  oven,  in  a  vacuum  over  sulphuric  acid,  and  at  100° — 
but  in  only  two  experiments  have  I  observed  the  formation 
of  fi-oxynitrohydrothymine.  The  conditions  under  which  I 
obtained  this  isomer  were  as  follows:  One  and  six- tenths 
grams  of  thymine  were  dissolved  in  8  cc.  of  cold,  fuming  nitric 
acid  (sp.  gr.  i .  5)  and  the  solution  was  allowed  to  evaporate 


Researches  on  Pyrimidines. 


35 


in  the  atmosphere  overnight.  The  following  morning  large, 
transparent  blocks  had  deposited,  which  showed  no  signs  of 
melting  at  i83°-i85°,  but  decomposed  at  2 30 °-2 3 5°,  accord- 
ing to  the  rate  of  heating.  One  of  the  crystals  selected  for 
analysis  weighed  0.2600  gram.  The  isomer  did  not  revert 
to  the  a  derivative  when  crystallized  from  water  or  absolute 
alcohol,  but  separated,  on  cooling,  in  well-developed  prisms 
decomposing  at  23o°-236°.  In  another  experiment,  0.5 
gram  of  thymine  was  dissolved  in  10  cc.  of  fuming  nitric  acid 
and  the  solution  allowed  to  evaporate  over  sulphuric  acid  in  a 
vacuum  desiccator.  I  obtained  practically  a  quantitative 
yield  of  the  /?  derivative  melting  at  23o°-235°.  The  com- 
pound did  not  lose  weight  when  heated  for  one-half  hour  at 
9o°-ioo°.  Analysis  (Kjeldahl) : 


N 


Calculated  for 
C5H706N8. 

22.22 


Found. 


I. 
22.00 


II. 
22.  I 


Reduction  of  [3-Qxynitrohydrothymine  with  Tin  and  Hydro- 
chloric Acid. — This  compound  was  reduced  in  the  same  man- 
ner as  the  a  derivative.  The  excess  of  tin  was  removed  with 
hydrogen  sulphide  and  the  filtrate  evaporated  to  dryness.  I 
obtained  a  crystalline  residue  which  separated  from  water 
in  plates  melting  at  3i5°-32o°.  The  compound  sublimed 
when  heated  in  a  test  tube,  and  when  mixed  with  thymine, 
the  melting  point  was  not  lowered.  It  dissolved  in 
fuming  nitric  acid,  giving  a-oxynitrohydrothymine  melting  at 
183 °-i85 °.  Analysis  (Kjeldahl) : 


N 


Calculated  for 
C6H602N2. 

22.22 


Found. 
22.31 


Rearrangement  of  fi-Oxynitrohydrothymine  into  a-Oxynitro- 
hydrothymine. — Some  of  the  a-pyrimidine,  melting  at  183°- 
185°,  was  preserved  in  a  desiccator  from  May  29,  1907,  until 
January  17,  1908.  It  apparently  underwent  no  change,  and 
melted  at  i8i°-i83°  with  effervescence.  A  sample  of  the 
/?-pyrimidine,  melting  at  23o°-235°,  was  preserved  from  June 
19,  1907,  to  October  7,  1907.  It  then  decomposed  at  227°- 
235°,  and  a  nitrogen  determination  (Kjeldahl)  gave  22.00 


36  Researches  on  Pyrimidines. 

per  cent;  calculated,  22.22  per  cent  nitrogen.  This  material 
was  not  examined  again  until  January  16,  1908.  It  then  had 
completely  rearranged  to  the  a-pyrimidine  and  melted  at 
i83°-i88°  with  effervescence.  A  mixture  of  this  material 
and  pure  a-oxynitrohydrothymine  melted  at  i83°-i86°  with 
effervescence.  Analysis  (Kjeldahl) : 

Calculated  for 

CsH7O5N3.  Found. 

N  22.22  21.9 

I  take  pleasure  in  thanking  Professor  W.  E.  Ford  for  the 
crystallographic  description  of  oxynitrohydrothymine  and 
also  Mr.  D.  B.  Jones  for  his  help  in  this  investigation. 

NEW  HAVEN,  CONN, 
Jan.  18,  1908. 


1 1 52  HENRY   L.    WHEELER   AND   LEONARD   M.    LIDDLE. 

[CONTRIBUTIONS  FROM  THE  SHEFFIELD  LABORATORY  OF  YALE  UNIVERSITY.] 

RESEARCHES  ON  PYR1MIDINES :  SYNTHESIS  OF  URACIL-3-ACETTC 

ACID. 

[THIRTY-FIRST   PAPER.] 

BY  HENRY  L.  WMKRLER  AND  LEONAI-D  M.  LIDDI.K. 
Received  May  8,  1908. 

Johnson  and  Heyl  found  when  methyl  iodide  and  2-ethylmercapto-6- 
oxypyrimidine  (for  nula  I)  are  warmed  in  alcoholic  solution  in  the  presence 
of  potassium  hydroxide,  that  the  methyl  group  substitutes  in  the  i-position 
of  the  pyrimidine  and  that  i -methyl- 2-ethylmercapto-6-oxypyrimidine, 
II,  results.1  The  formation  of  a  3-methyl  derivative  has  not  yet  been 
observed  in  this  reaction.  When  the  mercapto  derivative  was  warmed 
with  hydrochloric  acid,  i-methyl  uracil,  III,  was  obtained.  The  struc- 
ture of  this  methyl  uracil  was  settled  by  converting  it  into  i-methyl- 
5-nitro-6-oxypyrimidme  which  had  been  obtained  previously,  in  a  different 
manner  by  Behrend  and  Thurm.2 

We  have  obtained  an  entirely  different  result  when  2-ethylmercapto- 
6-oxypyrimidine  is  treated  with  ethyl  chloracetate  and  alkali  in  alcoholic 
solution.  The  alkylation  in  this  case,  although  under  similar  condi- 
tions, takes  place  in  the  3-position  and  2-ethylmercapto-6-oxypyrim- 
idine-3-ethyl  acetate,  IV,  is  formed. 

When  this  ester  is  warmed  with  alkali  it  dissolves  and  hydrochloric 
acid  then  precipitates  2-ethylmercapto-6-oxypyrimidine-3-acetic  acid, 
V.  If  this  acid  is  warmed  with  hydrochloric  acid,  rnercaptan  is  evolved 
and  uracil-3-acetic  acid  results,  VI. 

The  mercapto  acid,  V,  was  also  obtained  by  heating  2-ethylmercapto- 
6- oxy pyrimidine  in  alkaline  solution  with  potassium  chloracetate  and 
uracil-3-acetic  acid  can  be  directly  prepared  by  treating  uracil  in  alkaline 
solution  with  chloracetic  acid  At  this  point  it  seemed  possible  that 
alkyl  iodides  might  be  found  to  regularly  give  i-alkyl  derivatives.  We 
therefore  examined  the  action  of  ethyliodoacetate  on  uracil  and  it  was 
found  that  this  gave  the  same  acid  as  the  chlorine  compound. 

It  is  evident  from  these  results  that  the  structure  of  each  new  alkyl 
derivative  must  be  determined  separately  and  uracil-3-acetic  acid  should 
be  of  service  in  this  direction.3  The  proof  of  the  structure  of  the  acetic 
acid  compounds  was  obtained  as  follows:  Johnson  and  Heyl's  i-methyl- 
uracil,  III,  was  treated  with  chloracetic  acid  and  an  excess  of  alkali; 

1  THIS  JOURNAL,  37,  628  (1907). 

2  Ann.    (Liebig),  323,  160. 

3  The  above  results  also  show  that  alkylation  does  not  give  any  clue  to  the  posi- 
tion of  hydrogen  in  the  substance  alkylated.     Since  2-ethyl-mercapto-6-oxypyrimidine 
is  soluble  in  alkali  it  is  represented  as  having  the  NH-CO  group  with  hydrogen  in  the 
i -position. 


RESEARCHES    ON   PYRIMIDINES.  1  1  53 

this  gave  i-methyluracil-3-acetic  acid,  VII,  and  the  same  methyl  acid 
was  formed  when  our  uracil  acetic  acid,  VI,  was  methylated  with  methyl 
iodide  and  potassium  hydroxide  in  methyl  alcohol.  The  structure  of 
these  compounds  and  their  relations  are  expressed  in  the  following  for- 
mulas : 

HN—  CO  CH3N—  CO  CH3N—  CO 

II  II  II 

C2H5SC     CH  ->          C2H5SC     CH  ->  OC     CH 

I!     li  II     II  II 

N—  CH  N—  CH  HN—  CH 

L  IL 


N—  CO  N—  CO  HN—  CO  CH3N—  CO 

II      I  I!      I  II  II 

C2H5SC     CH  ->     C2H5SC     CH  ->  OC     CH  -^  OC     CH 

I       II  I      II  II  I       II 

2H5OCOCH2N—  CH     HOCOCH2N—  CH     HOCOCH2N—  CH     HOCOCH2N—  CH 

IV.  V.  VI.  VII. 

Experimental  Part. 

2-Ethylmercapto-6-oxypyrim'idine-3-ethyl  Acetate  (formula  IV,  above). 
Molecular  proportions  of  sodium,  2-ethylmercapto-6-oxypyrimidine  and 
ethylchloracetate  were  dissolved  in  alcohol,  in  the  order  named,  and 
the  mixture  was  warmed  until  it  no  longer  gave  an  alkaline  reaction 
(2-3  hours).  The  solution,  filtered  from  sodium  chloride,  gave  a  thick 
oil  on  evaporating  to  dryness.  When  this  was  shaken  with  ether  and 
water  it  deposited  prismatic  crystals.  The  material  was  crystallized 
from  water;  5  grams  dissolved  in  about  20  cc.  of  hot  water  and  on  cool- 
ing bunches  of  beautiful,  long,  colorless  prisms  separated  which  melted 
to  a  clear  oil,  without  effervescence,  at  129°.  Analysis: 

Calculated  for  C10H14O3N2S;  N2  11.57;  found,  11.87. 
This  ester  is  readily  soluble  in  alcohol  and  in  dilute  alkali. 

2-Ethylmercapto-6-oxypyrimidine-3-acetic  Acid  (formula  V).  —  The  solu- 
tion of  the  above  ester  in  dilute  alkali  gave  no  precipitate  when 
acidified  with  acetic  acid.  On  adding  hydrochloric  acid  in  slight  excess 
a  granular  precipitate  was  formed.  This  was  found  to  be  very  soluble 
in  hot  alcohol  and  moderately  so  in  cold.  It  is  difficultly  soluble  in 
water.  The  long,  slender  prisms  from  alcohol  had  a  fern-like  growth 
and  melted  at  208-209°  with  some  effervescence. 

Calculated  for  C8H10O3N2S:  N,  13.08;  found,  13.12. 

Five  grams  of  2-ethylmercapto-6-oxypyrimidine  were  dissolved  in  two 
molecular  proportions  (3.6  grams)  of  potassium  hydroxide  and  three 
grams  of  chloracetic  acid  in  5  cc.  of  water  were  added.  When  this  solu- 
tion was  evaporated  nearly  to  dryness  on  the  steam  bath,  1.5  grams 
of  unaltered  2-ethylmercapto-6-oxypyrimidine  separated.  The  solution 


1 1 54  HENRY   L.    WHEELER  AND   LEONARD   M. 

was  filtered,  made  alkaline  with  sodium  hydroxide  and  reheated  a  short 
time  on  the  steam  bath.  On  cooling  and  adding  hydrochloric  acid  3.1 
grams  of  the  above  mercapto  acid  were  obtained.  When  this  material 
was  warmed  with  strong  hydrochloric  acid,  on  the  steam  bath,  mercaptan 
was  evolved  and  uracil-3-acetic  acid  was  obtained. 

Uracil-3-acetic  Acid  (formula  VI). — The  above  mercapto  acid 
and  ester  are  quantitatively  converted  into  uracil-3-acetic  acid 
by  means  of  hydrochloric  acid.  It  was  found,  however,  that 
uracil-3-acetic  acid  could  be  more  conveniently  prepared  directly 
from  uracil  as  follows:  An  aqueous  solution  of  uracil  (10.2  grams) 
in  two  molecular  proportions  of  potassium  hydroxide  was  boiled 
with  the  calculated  quantity  of  chloracetic  acid.  When  the  solution 
gave  an  acid  reaction  it  was  made  alkaline  by  the  addition  of  a  few  drops 
of  potassium  hydroxide.  When  it  finally  remained  alkaline  after  10 
minutes  boiling,  it  was  cooled  and  acidified  with  hydrochloric  acid.  The 
yield  of  uracil-3-acetic  acid  (10.8  grams)  was  70  per  cent,  of  the  theoret- 
ical. The  acid  was  readily  soluble  in  hot  water  and  moderately  soluble 
in  cold.  It  formed  small  blocks  or  tables  which  melted  with  efferves- 
cence at  285°.  It  was  nearly  insoluble  in  methyl  or  ethyl  alcohol. 

Calculated  for  C6H6O4N2:  N,  16.47;  found,  16.57,  16.69. 

This  acid  showed  no  tendency  to  form  a  hydantoin.  It  was  found  to  be 
very  stable  when  heated  with  acids.  It  was  obtained  unaltered  when 
boiled  for  10  hours  with  hydrochloric  acid.  It  dissolved  in  boiling  acetic 
anhydride  and  on  evaporating  and  crystallizing  the  residue  from  85 
per  cent,  alcohol,  or  water,  unaltered  acid  was  obtained.  It  was  also 
obtained  unaltered  when  heated  with  20  per  cent,  sulphuric  acid  for  one 
and  a  half  hours  at  200°.  It  gave  no  color  with  bromine  water  and  barium 
hydroxide. 

The  potassium  salt  of  uracil-3-acetic  acid,  prepared  by  dissolving  the 
acid  in  the  calculated  quantity  of  potassium  hydroxide,  crystallized 
in  long,  flat  prisms  which  were  very  soluble  in  cold  water. 

The  copper  salt  was  obtained  as  a  minutely  crystalline  light  blue  salt 
on  mixing  a  solution  of  the  potassium  salt  with  one  of  copper  sulphate. 
Silver  and  zinc  sulphates  also  gave  crystalline  salts  while  the  precipitates 
obtained  with  mercuric  chloride  and  lead  acetate  were  amorphous. 

The  barium  salt  obtained  by  dissolving  the  acid  in  a  solution  of  barium 
hydroxide  and  then  removing  the  excess  of  barium  by  carbon  dioxide 
and  concentrating,  formed  balls  of  needles  like  uracil.  It  was  readily 
soluble  in  hot  water.  It  was  not  decomposed  by  acetic  acid. 

Calculated  for  (C6H3O4N2)2Ba:  N,  11.77;  found,  11.46. 


RESE ARCHES   ON    PYRIMIDINKS.  1 1 55 

HN— CO 

I         I 

Uracil-j-methylacetate,  OC      CH. — The     acid    (1.75    grams) 

I       II 
CH3OCOCH2N— CH 

was  esterified  in  methyl  alcohol  (50  cc.)  with  a  few  drops  of  concen- 
trated sulphuric  acid.  On  evaporating  to  about  15  cc.  and  cooling, 
1.2  grams  or  63  per  cent,  of  the  ester  separated.  It  was  readily 
soluble  in  hot  water  and  hot  alcohol.  It  formed  beautiful  color- 
less needles  and  although  it  was  repeatedly  crystallized  from  water 
it  melted  as  if  it  was  a  mixture,  partially  melting  at  about  177°,  then 
melting  to  a  clear  oil  at  about  216°.  Its  appearance  and  the  following 
nitrogen  determination  indicated  that  it  was  pure. 
Calculated  for  C7H8O4N2:  N,  15.29;  found,  15.13. 

HN  — CO 

I         I 
5-Bromuracil-  ^-acetic  Acid,  OC      CBr. — Two  grams  of  uracil- 

I         II 
HOCOCH2N  — CH 

3-acetic  acid  dissolved  in  water  were  treated  with  an  excess  of 
bromine  and  the  solution  was  then  allowed  to  evaporate  in  the 
air.  On  drying  the  residue  over  sulphuric  acid,  it  weighed  2.8 
grams  or  96  per  cent,  of  the  calculated  yield  for  a  monobrom  substitution 
product.  It  was  readily  soluble  in  hot  water,  difficultly  so  in  cold  and 
nearly  insoluble  in  alcohol.  It  formed  bunches  of  colorless  needles  which 
melted  with  effervescence  at  244°. 

Calculated  for  C6H3O4N2Br:  N,  11.24;  found,  11.58. 

HN— CO 

I       I 
$-Nitr  our  acil- 3-acetic  Acid,  OC     CNO2. — Two  grams  of  uracil- 

I       II 
HOCOCH2N— CH 

3-acetic  acid  were  treated  with  10  cc.  of  concentrated  nitric  acid 
and  5  cc.  of  concentrated  sulphuric  acid  on  the  steam  bath.  In 
twenty  minutes  a  crop  of  colorless  crystals  had  separated,  weighing 
1.75  grams  or  70  per  cent,  of  the  calculated  amount.  This  material 
was  readily  soluble  in  hot  water  and  difficultly  soluble  in  alcohol.  It 
formed  colorless  prisms  which  melted  with  effervescence  at  264-265°. 
Calculated  for  C6H5O6N3:  N,  19.55;  found,  19.66,  19.28. 

CH3N  — CO 

i -Methyluracil- 3-acetic  Acid,  OC       CH. — From    i-methyluracil'. 

I         II 
HOCOCH2N  — CH 

A  mixture  of  2.6  grams   methyl    uracil,    3    grams   of   chloracetic   acid 


1156  HENRY  L.    WHEELER   AND   LEONARD   M.    LIDDLE. 

and  3.2  grams  of  potassium  hydroxide  in  20  cc.  of  water  were 
warmed  on  the  steam  bath.  In  a  half  hour  the  solution  was  acid 
to  litmus.  It  was  made  alkaline  and  boiled  for  a  short  time.  On 
acidifying  the  solution  with  hydrochloric  acid  and  cooling,  crystals  sepa- 
rated; this  material  weighed  2.7  grams.  It  crystallized  from  water 
in  needle-like  prisms  or  in  prismatic  plates,  and  melted  constantly  at 
239°~~24O°  to  a  clear  oil  without  effervescence.  It  forms  beautiful,  trans- 
parent prisms  from  alcohol. 

Analysis  I. 

From  Uracil-3-acetic  Acid:  Uracil  acetic  acid  (1.2  grams)  and  four 
molecular  proportions  of  potassium  hydroxide  were  dissolved  in  a  little 
water.  An  excess  of  methyl  iodide  (5  grams)  was  added  and  sufficient 
methyl  alcohol  to  effect  solution.  The  mixture  was  allowed  to  stand  in 
a  warm  place  for  two  days  when  the  solution  was  acid  to  litmus.  It 
was  evaporated  to  dryness  and  the  residue  was  crystallized  from  water 
containing  a  little  sulphur  dioxide.  This  gave  0.6  gram  of  material 
crystallizing  in  thin  prismatic  plates  and  having  properties  identical 
with  the  acid  from  i-methyl  uracil.  When  these  substances  were  mixed, 
the  melting  point  was  not  lowered.  Analysis  II. 

Calculated  for  C7H8O4N2:    N,  15.21;  found:  I,  15.18;  II,  15.41. 

NEW  HAVEN,  CONN.,  May,  1908. 


[Reprinted  from  the  Journal  of  the  American  Chemical  Society.    Vol.  XXX. 
No.  7.    July,  1908.] 


[CONTRIBUTIONS  FROM  THE  SHEFFIELD  LABORATORY  OF  YALE  UNIVERSITY.] 

RESEARCHES  ON  P YRIMIDINES :  SYNTHESIS  OF  URACIL-4- ACETIC 

ACID. 

[THIRTY-SECOND  PAPER.] 

BY  HENRY  L-  WHEELER  AND  LEONARD  M.  LIDDLE. 
Received  May  8,  1908. 

Pinner  has  shown  that  acetone  dicarboxylic  ester  condenses  with 
benzamidine  giving  phenyloxypyrimidine  acetic  ester.1  He  also  found 
that  the  ester  condenses  with  other  aromatic  amidines  of  the  general 
formula,  R — C(NH2)NH.  Acetamidine  and  phenylacetamidine,  he  states 
did  not  give  crystalline  products. 

The  pseudothioureas  may  be  viewed  as  amidines  derived  from  the 
iminothiocarbonic  esters.  2-Kthylpseudothiourea  is  ethylthiocarbam- 
idine  or  mercaptof ormamidine : 

C2H5S— C(OR)NH    ->  C2H5S— C(NH2)NH. 

In  accordance  with  this  we  have  found  that  2-ethylpseudothiourea  con- 
denses very  smoothly,  in  alkaline  solution,  with  acetonediethylcarboxyl- 
ate,  yielding  2-ethylmercapto-6-oxypyrimidine-4-ethyl  acetate  (I).  The 
condensation  may  be  represented  as  follows: 

1  Ber.,  28,  480  (1895). 


RESEARCHES   ON   PYRIMIDINES.  1  1  57 

HNH       C2H5OCO  HN  —  CO  C,H5OH 

II  II 

C2H5SC        H-  CH  ==  C2H5SC       CH  + 

II  I!  '  II       II 

NH  HOCCH2C02C2H5  N  —  CCH2CO2C2H5    H2O 

I. 

When  this  pyrimidine  ester,  I,  is  warmed  with  aqueous  alkali  it  is  readily 
saponified,  and  on  acidifying  the  solution  with  hydrochloric  acid,  2- 
ethylmercapto-6-oxypyrimidine-4-acetic  acid,  II,  is  obtained.  When 
this  mercapto  acid  is  digested  on  the  steam  bath  with  concentrated 
hydrochloric  acid,  mercaptan  is  given  off  and  uracil-4-acetic  acid,  III, 
results. 

HN—  CO  HN—  CO 

I  I       I 

C2H5SC     CH  ->  OC     CH 

II       II  I       II 

N—  CCH2COOH  HN—  CCH2COOH 

TI- 


HN—  CO  HN—  CO 

II  II 

C2H5SC      CN  SC      CH 

II       II  I        II 

N—  CCH3  HN-CCH3 

IV.  V. 

On  melting  2-ethylmercapto-6-oxypyrimidine-4-acetic  acid,  carbon  diox- 
ide escapes  and  the  material  is  converted  into  2-ethylmercapto-4-methyl- 
6-  oxy  pyrimidine,  IV.  If  melted  in  a  stream  of  dry  hydrogen  chloride 
ethyl  chloride  is  given  off,  in  addition  to  carbon  dioxide,  and  2-thio- 
4-methyluracil,  V,  is  formed.  These  last  two  pyrimidines  have  been 
described  by  List1  who  obtained  them  in  a  different  manner. 

The  action  of  dry  hydrogen  chloride  on  the  mercaptopyrimidines, 
leading  to  the  formation  of  2-thiopyrimidines  with  loss  of  alkyl  halide, 
is  a  new  reaction  in  the  pyrimidine  series.  We  have  found  that  it  can 
be  applied  in  other  cases.  Taken  in  connection  with  the  action  of  dilute 
nitric  acid  (Marckwald2)  or  hydrogen  peroxide  (Traube3)  we  are  now 
able  to  replace  a  2-alkylmercapto  group  by  hydrogen.  This  is  of  im- 
portance for  synthetic  work  since  formamidine  has  not  yet  been  shown 
to  lend  itself  to  pyrimidine  condensations. 

Experimental  Part. 

HN  —  CO 

I  I 
2-Ethylmercapto-6-oxypyrimidine-4-ethylacetate,  C2H5SC       CH  .  —  Twelve 

II  II 

N—  CCH2C02C2H6 

1  Ann.  chem.  (Liebig),  236,  3  (1886). 

2  Ber.,  25,  3112  (1892). 

a  Ann.  chem.  (Liebig),  331,  71  (1904). 


1158  HENRY   L.    WHEELER   AND   LEONARD   M.    LIDDLE. 

grams  of  potassium  hydroxide  were  dissolved  in  20  cc.  of  water 
and  to  this  cold  solution  18.3  grams  of  the  ethyl  bromide  addition  prod- 
uct of  thiourea  were  added.  As  soon  as  solution  took  place,  20  grams 
of  acetone  diethylcarboxylate  were  slowly  added  and  the  mixture  was 
allowed  to  stand  for  about  an  hour,  then  warmed  for  a  short  time  on  the 
steam  bath.  On  cooling,  and  acidifying  with  acetic  acid,  17  grams  of 
the  condensation  product  separated.  This  was  found  to  be  very  soluble 
in  hot  alcohol,  hot  water  and  acetic  acid,  less  soluble  in  cold  alcohol 
and  nearly  insoluble  in  cold  water.  On  crystallizing  from  hot  alcohol 
long,  colorless,  silky  needles  were  obtained  which  melted  sharply  to  an 
oil  at  131°. 

Calculated  for  C10HUO3N2S:  N,  11.57;  found,  11.60,  11.67. 

HN—CO 

I       I 
2-Ethylmercapto-6-oxypyrimidine-4-acetic  acid,  C2H5SC      CH  . — 

N— CCH2COOH 

Two  grams  of  the  above  ester  were  dissolved  in  25  cc.  of  water  containing 
1.5  grams  of  potassium  hydroxide.  The  solution  was  heated  on  the  steam 
bath  for  a  half  hour,  then  cooled  and  the  acid  precipitated  with  hydro- 
chloric acid.  The  crystalline  precipitate  weighed  1.5  grams  or  86  per 
cent,  of  the  calculated.  It  was  readily  soluble  in  hot  alcohol  and  it  gave 
burrs  of  colorless  needles.  It  was  less  soluble  in  water  and  it  melted 
at  155°  with  vigorous  effervescence. 

Calculated  for  C8H10O3N.jS:  N,  13.08;  found,  13.10,  13.24. 
This  acid  is  not  precipitated  from  alkaline  solution  by  acetic  acid. 

One  gram  of  2-ethylmercapto-6-oxypyrimidine-4-acetic  acid  was  heated 
in  an  oil  bath  at  170°  until  effervescence  ceased.  The  residue  was  de- 
colorized with  charcoal  and  recrystallized  from  water.  It  melted  at 
145-147°,  and  when  mixed  with  2-ethylmercapto-4-methyl-6-oxy- 
pyrimidine  the  melting  point  was  not  altered.  One  gram  of  the  acid 
was  melted  in  an  oil  bath  at  170°  and  a  stream  of  dry  hydrogen  chlor- 
ide was  then  allowed  to  pass  over  the  substance.  It  immediately  solidi- 
fied. On  crystallizing  from  water,  it  formed  colorless  prisms  which  gave 
a  strong  test  for  sulphur.  This  material  had  all  the  properties  of  2-thio- 
4-methyluracil.  Analysis : 

Calculated  for  C5H6ON2S:  N,  19.71;  found,  19.78. 
HN  —  CO 

I         I 
Uracil-4-acetic  acid,  OC        CH.H2O. — When  the  above  mercapto  acid 

I          II 
HN  —  CCH2COOH. 

was  warmed  on  the  steam    bath    with  concentrated  hydrochloric   acid, 
it  readily  evolved  mercaptan  and  gave  a  quantitative  yield  of   uracil- 


RESEARCHES   ON    PYRIMIDINES.  1 1  59 


4- ace  tic  acid.  The  acid  was  crystallized  from  water.  It  formed  flat 
prisms  which  sintered  above  300°  and  melted  with  effervescence  at  340°. 
In  concentrated  aqueous  solution,  it  separates  at  first  in  an  anhydrous 
condition  then  in  crystals  containing  one  molecule  of  water. 

Calculated  for  C6H6O4N2.H2O :  H2O  =  9.57;  found,  9.97. 
Calculated  for  C6H6O4N2:  N,  16.47;  found,  16.95. 

Uracil-4-acetic  acid  is  soluble  in  about  8  parts  of  boiling  water  and 
in  30  parts  of  cold.  It  is  much  less  soluble  in  alcohol.  It  is  a  strong 
acid  and  the  aqueous  solution  reddens  litmus.  It  does  not  give  a  pre- 
cipitate with  barium  chloride  or  mercuric  chloride.  It  forms  an  amor- 
phous silver  salt  soluble  in  ammonia. 

The  Potassium  Salt,  CCH5O4N2K. — Two  grams  of  the  acid  were  dis- 
solved in  a  little  water  containing  0.7  gram  of  potassium  hydroxide. 
On  adding  alcohol,  balls  of  a  minute,  colorless  crystal  separated.  The 
salt  was  very  soluble  in  water  and  insoluble  in  alcohol.  It  was  dried 
in  a  desiccator  for  analysis. 

Calculated  for  C6H5O4N2K :  N,  13.46;  found,  13.40. 
HN— CO 

I       I 
Uracil-4-methylacetate,   OC      CH  . — Bight- tenths    gram     of 

II 
HN-CCH2COOCH3 

anhydrous  acid  was  esterified  by  dissolving  in  15  cc.  of  methyl 
alcohol  containing  two  drops  of  concentrated  sulphuric  acid  and 
warming  the  solution  for  one  hour.  On  concentrating  the  solution 
to  about  7  cc.,  0.5  gram  of  ester  separated.  The  material  was  washed 
with  water  and  recrystallized  from  water.  It  then  formed  large,  elon- 
gated, six-sided  prisms  which  melted  to  an  oil  at  216-218°  with  slight 
effervescence.  It  was  very  soluble  in  hot  water  and  hot  alcohol.  It 
was  dried  over  sulphuric  acid  for  analysis. 
Calculated  for  C7H8O4N2:  N,  15.21;  found,  15.39. 

HN  — CO 

I 
Uracil-^-ethylacetate,    OC       CH.H2O. — Two   grams    of    uracil-4- acetic 

I         II 
HN  --  CCH2COOC2H5 

acid  were  dissolved  in  25  cc.  of  absolute  alcohol  containing  several 
drops  of  concentrated  hydrochloric  acid  and  the  solution  was  boiled  for 
three  hours.  It  was  then  evaporated  to  dryness  and  the  residue  crystal- 
lized three  times  from  about  90  per  cent,  alcohol.  There  was  then  ob- 
tained about  0.8  gram  of  ester.  It  was  very  soluble  in  hot  alcohol  and  it 
separated,  on  cooling,  in  colorless  prisms,  which  curiously  contained  a 
molecule  of  water  of  crystallization.  This  is  the  first  pyrimidine  ester 


Il6o  RESEARCHES  ON    PYRIMIDINES. 

that  has  been  found  to  have  water  of  crystallization.  It  melted  to  an 
oil  at  187-189°.  It  was  dried  over  sulphuric  acid  for  analysis. 

Calculated  for  C8H10O4N2.HaO:  H2O  =  8.33;  found,  8.25;  N  =  12.96;  found,  12.97. 

HN— CO 

I        I 
5-Nitrouracil-4-acetic    acid,    OC      CNO2  . — Uracil-4-acetic    acid 

I       II 
HN— CCH2COOH 

was  nitrated  by  dissolving  i  gram  of  the  acid  in  4  cc.  of  a  mixture  of 
two  parts  concentrated  nitric  acid  and  one  of  sulphuric  acid.  The  solu- 
tion was  then  heated  on  the  steam  bath.  The  product  was  insoluble  in 
alcohol  and  difficultly  soluble  in  hot  water.  It  formed  minute  cubes 
which  melted  with  effervescence  at  153°. 

Calculated   for  C6H5O6N3:  N,  19.53;  found,  19.39. 

HN  — CO 

I 
Dibromoxyhydrouracil-4-acetic  acid,  OC       CBr2. — One  gram  of  uracil- 

HN  —  C(OH)CH2COOH 

4-acetic  acid  was  dissolved  in  water  and  a  large  excess  of  bromine  was 
added.  On  spontaneous  evaporation  colorless,  elongated  plates  sepa- 
rated. They  became  dark  colored  above  180°  and  melted  with 
effervescence  at  240°.  The  substance  appears  to  crystallize  with 
a  half  molecule  of  water  of  crystallization. 

Calculated  for  C6H6O5N2Brr V,,H2O :  H2O  =  2.54;  found,  2.89.     N  =  7.87,  found, 
7-55- 

A  nitrogen  determination  in  the  case  of  the  substance  dried  at  106° 
gave  8.43  per  cent,  nitrogen  while  the  calculated  is  8.10  per  cent. 

NEW  HAVEN,  CONN.,  May,  1908. 


IX.    RESEARCHES  ON  PYRIMIDINS:  SYNTHESES  OF  SOME 

NITROGEN- ALKYL  DERIVATIVES  OF  CYTOSIN, 

THYMIN  AND  URACIL. 

(Thirty- third  Paper.) 

BY  TREAT  B.  JOHNSON  AND  SAMUEL  H.  CLAPP. 

(From  the  Sheffield  Laboratory  of  Yale  University.) 

(Received  for  publication,  May  28,  1908.) 

The  nitrogen-methyl  derivatives  of  cytosin,  thymin  and  uracil 
are  of  especial  interest  because  of  the  occurrence  of  methyl- 
purins  in  nature.  Purins  may  be  considered  as  compound  rings 
in  which  imidazol  has  been  grafted  into  pyrimidins.  A  similar 
relationship  exists  between  3-methyluracil,  IV,  1,3 -dimethyl  - 
uracil,  VI,  and  the  purins,  theobromin,  III,  theophyllin,  V, 
and  caffein,  VII,  as  exists  between  uracil,  II,  and  xanthin,  I. 


NH— CO 

I          I 
CO       CNH 


\ 


CH 


NH— CN  ' 
I 

NH— CO 

I          I 
CO      CNCH3 


NH— CO 

I  I 

CO       CH 

!       II 

NH— CH 
II 

NH— CO 

I  1 

CO      CH 


CH3N  CN/ 
III 

on3i\  Lxti 
IV 

CH3N- 

—CO                            CH3N—  CO 

i        i 

CH3N—  C 

CO  CNHv                              CO    CH 

CO  C 

^                        i 

CH3N- 

I        /                     CH3N—  CH 
-CN 
V                                        VI 

1 

CH3N—  C 
VU 

49 


50  Researches    on   Pyrimidins 

These  alkyl  derivatives  are  also  of  interest  because  of  the 
possibility  that  future  investigations  may  show  the  presence 
of  methylpyrimidins  in  animal  or  vegetable  organisms.  It  is 
interesting  to  note  here  that  Suzuki,  Aso  and  Mitarai,1  in  a 
paper  titled  "Ueber  die  chemische  Zusammensetzung  der 
japanischen  Sojasauce  oder  Schoyu,"  have  described  a  decom- 
position product  of  Schoyu  to  which  they  have  assigned  the 
empirical  formula  C6H9N3.  They  state  that  the  compound  is 
probably  an  isomer  of  aminodimethyl  pyrimidin.2 

We  shall  describe  in  this  paper  the  syntheses  and  properties 
of  3-methylcytosin,  VIII,  i-methylthymin,  IX,  3 -methyl thy min, 
X,  i,3-dimethylthymin,  XI,  and  i,3-dimethyluracil,  VI. 

N=C.NH2          CH3N CO  NH CO 

I        I 
CO    CH 

I        II 
CH3.N—  CH 

VIII 

CH3N— CO 

I       I 
CO   CCH3  CO  CH 

I       II  I       II 

CH3N— CH  CH3N— CH 

XI  VI 

Two  nitrogen-methyl  derivatives  of  thymin  and  uracil  have 
been  described  in  the  literature,  viz:  1,3 -dimethyl  thy  min,  XI, 
and  i-methyluracil,  XII.  Dimethylthymin3  was  prepared  by 
heating  the  mono-potassium  salt  of  thymin  with  methyliodide 
at  150°.  We  prepared  this  compound  and  also  i,3-dimethyl- 
uracil,  VI,  by  warming  thymin  and  uracil  respectively  in  alco- 
holic solution  with  the  required  proportions  of  potassium 
hydroxide  and  methyliodide. 

i-Methyluracil,  XII,  was  described  in  a  paper  from  this 
laboratory4  and  was  prepared  in  the  following  manner: 

1  C.  Blatt:  ii,  1649,  I9°7-     Bull.  College  Agr.,  Tokio,  vii,  477. 

2  Schwarze:  Journ.  f.  prakt.  Chem.,  xlii,  p.  i;  Schlenker:  Ber.  d.  deutsch, 
chem.  Gesellsch.,  xxxiv,  p.  2819;  Schmidt:  ibid.,  xxxv,  p.  1577. 

3  Steudel:  Zeitschr.  physiol.  Chem.,  xxx,  p.  539. 

4  Johnson  and  Heyl:  Amer.  Chem.  Journ.,  xxxvii,  p.  628. 


Treat  B.  Johnson  and  Samuel  H.  Clapp         51 

i-methyl-2-pseudoethylthiourea  was  condensed  with  the  sodium 
salt  of  ethyl  formylacetate  giving  i  -methyl- 2 -ethylmercapto-6- 
oxypyrimidin,  XIV.  This  same  mercaptopyrimidin  was  also 
obtained  by  treatment  of  2-ethylmercapto-6-oxypyrimidin,  XIII, 
with  methyliodide  in  presence  of  alkali.  Hydrolysis  of  this  mer- 
captopyrimidin with  hydrochloric  acid  gave  i-methyluracil,  XII. 

NH— CO  CH3N— CO  CH3N CO 

II  II  II 

C2H5SC        CH     ->     C2H6SC     CH     ->  CO     CH 

II          II  II       II  I          II 

N CH  N— CH  NH— CH 

XIII  XIV  XII 

We  now  find  that  2-ethylmercapto-5-methyl-6-oxypyrimidin 
XV,  reacts  with  methyliodide  in  presence  of  potassium  hydroxide 
giving  about  equal  proportions  of  the  two  isomeric  pyrimidins — 
i,5-dimethyl-2-ethylmercapto-6-oxypyrimidin,  XVI  (m.  65°)  and 
3,5-dimethyl-2-ethylmercapto-6-oxypyrimidin,  XVII  (m.  156°). 
Hydrolysis  of  these  mercaptopyrimidins  with  concentrated 
hydrochloric  acid  gave  i-methylthymin,  XVIII  (m.  202°  to 
205°)  and  3 -methyl thymin,  XIX  (m.  280°  to  282°),  respectively. 

NH— CO 

C2H5SC         CCH3 

II          II 

N CH 

XV 


CH3N—  CO 

1 
C2H5SC     CCH3 

II       II 

N—  CO 

II 
C2H5SC      CCH3 

1       II 

II       II 
N—  CH 
XVI 

1       II 
CH3N—  CH 

XVII 

1 

PM  N            PO 

1 
NH—  CO 

CO       CCH3 

CO      CCH3 

NH— CH  CH3N CH 

XVIII  XIX 


52  Researches    on   Pyrimidins 

The  structures  of  the  isomeric  methylthymins  and  incidentally 
the  corresponding  mercaptopyrimidins  were  established  in  the 
following  manner :  Wheeler  and  Johnson1  have  shown  that  cyto- 
sin  reacts  smoothly  with  bromine  water  giving  oxydibromhydro- 
uracil,  XX.  When  this  hydropyrimidin  was  digested  with 
alcohol  it  was  converted  quantitatively  into  5-bromuracil, 
XXI.  Since  the  6-amino  radical  is  removed  by  this  treatment, 

N— CNHa  NH— CO  NH— CO 

I  I  II  II 

CO       CH          ->      CO       CBr2         -»      CO      CBr 

I  II  II  I  II 

NH— CH  NH— CHOH  NH     CH 

XX  XXI 

it  seemed  probable  to  the  writers  that  substituted  cytosin 
derivatives  would  behave  in  a  similar  manner  giving  substituted 
uracils.  Our  experimental  data  confirms  this  assumption.  We 
find  that  cytosin  reacts  with  methyliodide  in  presence  of  po- 
tassium hydroxide  giving  3-methylcytosin,  VIII.  This  pyri- 
midin  reacted  with  bromine  water  giving  a  quantitative  yield  of 
3-methyloxydibromhydrouracil,  XXII.  When  this  hydropyri- 
midin was  warmed  with  alcohol  it  was  converted  into  3 -methyl  - 
5-bromuracil,  XXIII,  melting  at  255°  to  260°.  The  isomeric 
i-methyl-5-bromuracil2  XXIV,  melts  at  2 2 8°  to  229°.  5-Methyl- 
cytosin  apparently  reacts  with  methyliodide  in  a  similar  man- 
ner as  cytosin  giving  3,  5-dimethylcytosin,  XXV.  When  this 

N— CNH2  NH— CO  NH— CO     CH3N CO 

II  II  I  I  I  I 

CO        CH      — >          CO       CBr2     — >          CO      CBr  CO       CBr 

I            II                                                               I  II  I  II 

CH3N CH  CH3N CHOH       CH3N CH  NH— CH 

VIII  XXII  XXIII  XXIV 

pyrimidin  was  treated  successively  with  bromine  water  and 
alcohol,  it  was  converted  quantitatively  into  3-methylthymin, 
XIX,  melting  at  280°  to  282°.  This  result  also  proves  that  the 

1  This  Journal,  iii,  p.   183. 

2  Johnson  and  Heyl :  Loc.  cit. 


Treat  B.  Johnson  and  Samuel  H.  Clapp         53 


N=CNH2 

I        I 
CO    CCH3 

I        II 
CH3N— CH 

XXV 


NH— CO 


NH— CO 

I  I 

CO       CCH3 

I  II 

CH3N CH 

XIX 


mercaptopyrimidin,  XVII,  which  melts  at  156°,  is  a  3-methyl 
derivative  since  it  gives  3-methylthymin  on  hydrolysis. 

The  introduction  of  methyl  groups  into  uracil,  thymin,  and 
cytosin,  has  a  similar  influence  on  their  physical  properties  as 
in  the  case  of  purins.  They  increase  the  solubility  and  lower 
the  melting  points.  For  example:  while  uracil  and  thymin  are 
difficultly  soluble  in  alcohol,  the  methyl  derivatives  of  these 
pyrimidins  dissolve  easily  in  this  solvent  and  are  moderately 
soluble  in  cold  water.  The  3-methyl  derivatives  of  2 -ethyl  - 
mercapto-5-methyl-6-oxypyrimidin,  thymin  and  5-bromuracil 
are  more  soluble  in  water  than  the  isomeric  i-methylpyrimidins. 

It  is  also  interesting  to  note  that  the  3-methylpyrimidins 
melted  higher,  in  every  series  examined,  than  the  isomeric 
i-methylpyrimidins : 


2-  E  thy  Imercap  to- 1 , 5-  dimethy  1- 
6-oxypyrimidin. 

(65°) 
1-Methylthymin. 

(202°  to  205°) 
1  -  Methy  loxynitrohy  dro  thymin. 

(135°  to  136°) 

l-Methyl-5-bromuracil. 

(228°  to  229°) 


2-Ethylmercapto-3,5-dimethyl- 
6-oxypyrimidin. 

(156°) 
3-Methylthymin. 

(280°  to  282°) 
3-Methyloxynitrohydrothymin. 

(178°  to  181°) 

3-  Methyl-  5-bromuracil . 

(255°  to  260°) 


i-Methylthymin  and  3-methylthymin  reacted  in  a  similar 
manner  with  fuming  nitric  acid  as  thymin  giving  characteristic 
oxynitrohydrothymins,1  XXVIII  and  XXIX. 

CH3N CO  NH— CO 

I  I        otr  I  I        otr 

I      /CH3  ,CH3 

CO        C<                       and                   CO      C/ 
I             |    XN02                                       |  |   \N02 

NH—  CHOH  CH,N CHOH 


XXVIII 


XXIX 


1  Johnson:   Atner.  Ghent.  Journ.,  xl;  This  Journal,  iv,  p.  407, 


54  Researches    on   Pyrimidins 

Conductivity  measurements  on  thymin  and  its  methyl  deriva- 
tives disclosed  the  interesting  facts  that  thymin  and  i,3-dimeth- 
ylthymin  gave  practically  constant  conductivities  at  25°.  On  the 
other  hand,  i -methyl thymin  and  3-methylthymin  gave  abnormal 
conductivities  which  increased  with  the  length  of  time  these 
pyrimidins  were  kept  in  solution  (see  Appendix) .  This  inter- 
esting behavior  is  possibly  due  to  a  slow  hydrolysis  of  the 
pyrimidin  ring  giving,  in  solution,  /?-uraminoacrylic  acids, 
XXVI  and  XXVII. 


N(CH3).CO.NH.CH:C(CH3).CO-^CH3NH.CO.NH.CH:C(CH3).COOH. 

J I 

XXVI 

123         456 

NH.CO.N(CH3)CH:CH.CO      — >     H2N.CO.N(CH3).CH:C(CH3).COOH 

! I 

XXVII 

The  methyl  derivatives  of  thymin,  described  in  this  paper, 
should  be  of  interest  to  the  pharmacologist.  It  is  a  well  known 
fact  that  the  methylated  dioxypurins  possess  a  pronounced 
diuretic  action.  Sweet  and  Levene1  have  recently  shown  that 
the  administration  of  thymin  to  a  dog  also  caused  a  most  pro- 
nounced diuresis.  Whether  the  methylated  thymin  will  possess 
a  higher  diuretic  action  than  thymin  must  be  decided  by  further 
study. 

EXPERIMENTAL    PART. 

2-Ethylmercapto-i,5-dimethyl-6-oxypyrimidin: 

CH3N— CO 

I  I 
C2H5S.C     C.CH3 

II  II 
N— CH 

Five  grams  of  2-ethylmercapto-5-methyl-6-oxypyrimidin  and 
a  molecular  proportion  of  potassium  hydroxide  (1.6  grams) 
were  dissolved  in  boiling  95  per  cent  alcohol.  An  excess  of 

1  Journ.  of  Eocper.  Med.,  ix,  p.  229. 


Treat  B.  Johnson  and  Samuel   H.  Clapp         55 

methyliodide  was  then  added  and  the  solution  boiled  for  about 
one  hour  when  it  no  longer  reacted  alkaline  to  turmeric.  The 
undissolved  potassium  iodide  was  filtered  off  and  the  filtrate 
heated  on  the  steam-bath  to  remove  the  excess  of  alcohol.  We 
obtained  an  oily  residue,  which  deposited  a  mixture  of  2 -ethyl  - 
mercapto-i,5-dimethyl-6-oxypyrimidin  and  unaltered  2 -ethyl  - 
mercapto-5-methyl-6-oxypyrimidin,  when  triturated  with  cold 
water.  The  filtrate  contained  the  isomeric  2-ethylmercapto- 
3,5-dimethyl-6-oxypyrimidin  (see  below).  2-Ethylmercapto- 
i,5-dimethyl-6-oxypyrimidin  was  freed  from  the  unaltered 
material  by  treatment  with  a  small  volume  of  a  cold,  dilute 
solution  of  sodium  hydroxide.  The  weight  of  the  crude  pyri- 
midin  was  2.1  grams  or  30  per  cent  of  the  theoretical.  It  was 
purified  for  analysis  by  crystallization  from  hot  water,  and 
separated,  on  slow  cooling,  in  long,  slender  prisms  which  melted 
at  65°  to  a  clear  oil  without  effervescence.  It  did  not  contain 
water  of  crystallization.  It  was  dried  for  analysis  over  sulphuric 
acid  (Kjeldahl) : 

Calculated  for 
C8HI2ON2S:  Found: 

N 15.22  15.17 

2-Ethylmercapto-3 ,  f -dimethyl-  6-oxypyrimidin : 

N— CO 

II       I 
C2H5SC      CCH3 

I       II 
CH3N— CH 

In  order  to  isolate  this  pyrimidin  from  the  above  filtrate,  the 
solution  was  evaporated  to  dryness  and  the  residue  extracted 
several  times  with  cold  chloroform.  When  the  chloroform 
was  evaporated,  at  ordinary  temperature,  1.8  gram  of  the 
crude  pyrimidin  were  obtained,  or  33.4  per  cent  of  the  theo- 
retical. The  compound  crystallized  from  benzene  in  prisms 
which  melted  at  156°  to  a  clear  oil  without  effervescence.  It 
was  dried  for  analysis  over  sulphuric  acid  (Kjeldahl) : 

Calculated  for 
C8H12ON2S:  Found: 

N.  15.22  15.20 


56  Researches    on   Pyrimidins 

j  ,  ^-Dimethyl-  2  ,  6-dioxy  pyrimidin  (  i-methylthymin)  : 

CH3N  --  CO 

I  I 

CO      CCH3 

I  II 

NH—  CH 

A  quantitative  yield  of  this  pyrimidin  was  obtained  when 
2-ethylmercapto-i,5-dimethyl-6-oxypyrimidin  was  digested  with 
hydrobromic  acid  until  the  evolution  of  ethylmercaptan  ceased 
(8  hours).  The  acid  solution  was  then  evaporated  to  dryness 
and  the  pyrimidin  crystallized  from  water.  It  separated  in 
aggregates  of  stout  prisms  which  melted  at  202°  to  205°,  with 
effervescence,  to  a  clear  oil.  The  compound  was  readily  soluble 
in  boiling  alcohol  and  acetone.  It  did  not  contain  water  of 
crystallization.  Analysis  : 

0.2680  gram  of  substance  gave  0.5081  gram  of  CO2  andO.1379  gram  H2O. 

Nitrogen  determination  (Kjeldahl)  : 

Calculated  for  Found: 

CeH8O2N2:  I.  II.  III. 

C  ........................        51.43          51.71 

H  ........................          5.71  5.71 

N  ........................        20.00  20.07     20.07 

5  ,  ^-Dimethyl-  2  ,  6-dioxypyrimidin  (^-methylthymiri)  : 


I  I 

CO      CCH3 

I  II 

CH3N  -  CH 

This  pyrimidin  was  not  the  only  product  formed  when 
2-ethylmercapto-3,5-dimethyl-6-oxypyrimidin  was  digested  with 
hydrobromic  acid  for  5  hours.  When  the  acid  solution  was 
evaporated  to  dryness,  we  obtained  a  mixture  of  3  -methyl  - 
thymin  and  a  compound  which  was  difficultly  soluble  in  cold 
water.  The  latter  was  soluble  in  warm  alcohol  and  crystallized 
from  hot  water  in  needles  melting  at  229°  to  230°,  without 
effervescence  to  a  clear  oil,  It  was  soluble  in  alkalies  and  gave 
a  strong  test  for  sulphur.  The  analytical  determinations  indi- 


Treat  B.  Johnson  and  Samuel   H.  Clapp         57 

cated  that  the  compound  was  2-ihio-^  ^-dimethyl- 6-oxypyrimidin. 
Analysis  (Kjeldahl) : 

NH— CO 

i          I 
CS      CCHS 

I  II 

CH3N CH 

Calculated  for  Found: 

C6H8ON2S:  I.  II. 

N 17.95  18.4     18.3 

3-Methylthymin  is  more  soluble  in  cold  water  than  this 
2-thiopyrimidin  and  separated,  nearly  pure,  when  the  aqueous 
nitrates  (above)  were  concentrated  and  cooled.  It  was  purified 
for  analysis  by  recrystallization  from  water  and  melted,  when 
heated  slowly,  at  280°  to  282°  to  a  clear  oil.  This  pyrimidin 
showed  a  very  characteristic  behavior  when  crystallized  from 
hot  water.  When  the  hot,  saturated,  aqueous  solution  was 
quickly  cooled,  the  pyrimidin  separated  immediately  as  a  bulky, 
homogeneous  mass  of  long,  prismatic  needles.  On  standing, 
these  prisms  soon  disintegrated,  apparently  redissolved,  and 
were  replaced  by  characteristic  octahedral  prisms.  The  trans- 
formation was  complete  in  a  few  minutes.  The  compound 
did  not  contain  water  of  crystallization.  Analysis  (Kjeldahl) : 

Calculated  for 

C6H8O2N2:  Found: 

N 20.00  19.91 

i-Methyl-5-brom-4.-oxyhydrothymin: 

CH3N CO 

I  I    /CH3 

CO       C< 
I  lXBr 

NH—  CHOH 


This  compound  was  obtained  when  i-methylthymin  was  dis- 
solved in  an  excess  of  bromine  water  and  the  solution  allowed 
to  evaporate  in  a  vacuum  over  sulphuric  acid.  It  crystallized 
from  bromine  water  in  stout  prisms  and  melted,  on  slow  heating, 


58  Researches    on   Pyrimidins 

at  about  123°  to  125°  to  a  clear  oil.     It  was  dried  for  analysis 
over  sulphuric  acid  (Kjeldahl)  : 

Calculated  for 


Found: 
N  ................................         11.81  11.92 

i-Methyl-^-nitro-^-oxykydrothymin: 

CH3N  -  CO 

I  I/CH, 

CO  C< 

I  |XN02 

NH—  CHOH 

This  compound  was  prepared  by  dissolving  i  -methyl  thymin 
in  a  small  volume  of  fuming  nitric  acid  (sp.  gr.  1.5)  and  allowing 
the  solution  to  evaporate  spontaneously  in  the  air.  It  deposited 
in  well-developed  prisms  melting  at  about  135°  to  136°  with 
effervescence.  Analysis  : 

I.     0.0844  gram  substance  gave  15.5  cc.  moist  N2  at  21°  and  728  mm. 
II.     Nitrogen  determination  (Kjeldahl): 

Calculated  for  Found: 

C6H9O5N3:  I.  II. 

N  ........................       20.69  20.84     21.1 

j-Methyl-j-  nitr  o-  ^.-oxyhydrothymin  : 

NH—  CO 

I  I/CH, 

CO       C<         .H2O 
I  |XN02 

CH3N  -  CHOH 

This  pyrimidin  was  prepared  in  the  same  manner  as  its  isomer. 
It  separated  in  large  prisms  which  decomposed  at  about  178° 
to  181°  with  effervescence.  This  decomposition  point  varies 
according  to  the  rate  of  heating.  A  nitrogen  determination 
indicated  that  the  compound  contained  one  molecule  of  water  of 
crystallization.  It  slowly  underwent  decomposition  when  heated 
at  100°.  Analysis  (Kjeldahl)  : 

Calculated  for         Calculated  for 
C6HS05N3.H20:  CcH^Nv         Found: 

N..  19.00  20.69          18.74 


Treat  B.  Johnson  and  Samuel  H.  Clapp         59 

Mono-potassium  salt  of  tkymin: 

KN CO 

I  I 

CO      C.CH3 

I  II 

NH — CH 

Finely  pulverized  thymin  and  a  molecular  proportion  of 
potassium  hydroxide  were  dissolved  in  boiling  absolute  alcohol 
and  the  solution  boiled  for  four  hours.  The  potassium  salt 
separated,  on  cooling,  in  long  needles.  It  was  purified  for  analy- 
sis by  recrystallization  from  95  per  cent  alcohol.  Nitrogen 
determinations  in  the  salt,  dried  to  a  constant  weight  at  110°, 
agreed  with  the  calculated  value  in  a  mono-potassium  salt  of 
the  closed  ring  (Kjeldahl) : 

Calculated  for  Found: 

C5H5O2N2K:  I.  II. 

N 17.07  17.22     17.32 

/,  3-Dimethylthymin: 

CH3N— CO 

I        I 
CO    C.CH3 

I        II 
CH8N— CH 

This  pyrimidin  was  first  described  by  Steudel.1  We  obtained 
the  same  derivative,  in  a  smooth  manner,  under  the  following 
conditions:  Five  grams  of  thymin  and  4.6  grams  of  potassium 
hydroxide  were  dissolved  in  90  cc.  of  95  per  cent  alcohol  and 
an  excess  of  methyl  iodide  added  to  the  warm  solution.  The 
solution  was  boiled  for  twenty  minutes,  then  evaporated  to 
dryness,  and  the  crystalline  residue  extracted  several  times 
with  cold  chloroform  When  the  chloroform  was  evaporated 
we  obtained  2 . 7  grams  of  the  dimethyl  pyrimidin.  It  was 
very  soluble  in  water  and  chloroform  and  difficultly  soluble  in 
ether  and  petroleum  ether.  It  crystallized  from  alcohol  in 

1  Loc.  cit. 


60  Researches    on   Pyrimidins 

long  needles  melting  sharply  at  153°  to  a  clear  oil.     Analysis 
(Kjeldahl)  : 

Calculated  for 
C7Hi0O2N2:  Found: 

N  ................................         18.18  18.32 

/  ij-Dimethyl-f-brom-  ^.-oxyhydrothymin  : 

CH3X—  CO 

I/CH, 

CO  C< 

I          \Br 
CH3N—  CHOH 

Was  prepared  by  dissolving  i,  3-dimethylthymin  in  bromine 
water.  When  the  aqueous  solution  was  concentrated  in  a 
vacuum,  the  pyrimidin  separated  in  prisms  melting  at  132°  to 
133°  to  a  clear  oil.  Analysis  (Kjeldahl): 

Calculated  for 


Found  : 
N  ................................          11.16  11.25 

Mono-potassium  salt  of  uracil: 

KX  --  CO 

I  I 

CO       CH.H20 

I  II 

NH—  CH 

One  molecular  proportion  of  potassium  hydroxide  was  dissolved 
in  450  cc.  of  absolute  alcohol  and  13  grams  of  finely  pulverized 
uracil  suspended  in  the  solution.  After  digesting  for  eight  hours 
the  uracil  was  completely  changed  into  the  potassium  salt. 
It  was  difficultly  soluble  in  absolute  alcohol  and  very  soluble 
in  cold  water.  It  separated  from  dilute  alcohol  in  balls  of  long 
needles.  The  yield  was  quantitative.  The  salt  contained  one 
molecule  of  water  of  crystallization  which  was  determined  by 
heating  at  120°. 

I.  0.3365  gram  substance  lost  0.0351  gram  H2O. 
II.  0.2871     "  «  "     0.0302      " 

Calculated  for  Found: 

C4H3O2N2K.H2O:  I.  II. 

H2O  ....................    10.70          10.43  10.52 


Treat  B.  Johnson  and  Samuel  H.  Clapp         61 

Nitrogen  determination  in  salt  dried  at  160°  (Kjeldahl): 


N. 


Calculated  for 
C4H302N2K: 

18.67 


Found : 
I.  II. 

18.51     18.55 


Potassium  determination  in  the  hydrous  salt: 
0.1727  gram  substance  gave  0.0775  gram  KC1. 


K. 


Calculated  for 
C4H302N2K.H20: 

23.21 


Calculated  for 
C4H302N2K: 

25.98 


Found : 
23.55 


Nitrogen  determination  in  hydrous  salt  (Kjeldahl) : 


X. 


Calculated  for 
C4H3O2N2K.H2O: 

16.67 


Calculated  for 
C4H302N2K: 

18.65 


Found : 
16.81 


i  ,3-Dimethyluracil : 

CH3N— CO  ' 

I        I 
CO    CH 

I        II 
CH8N—  CH 

This  compound  was  prepared  by  warming,  in  alcoholic  solution, 
molecular  proportions  of  potassium  hydroxide  and  the  potas- 
sium salt  of  uracil  with  an  excess  of  methyliodide.  After 
boiling  for  three  hours  the  solution  was  evaporated  to  dryness 
and  the  pyrimidin  extracted  with  chloroform.  It  crystallized 
from  a  mixture  of  alcohol  and  ether  in  long,  slender  prisms  which 
melted  at  121°  to  122°.  It  was  extremely  soluble  in  cold  water, 
alcohol  and  chloroform,  but  insoluble  in  ether  and  petroleum 
ether.  Nitrogen  (Kjeldahl) : 


Calculated  for 


I. 


Found : 
II.  III. 


N. 


20.00 


20.05     20.06     20.24 


i,3-Dimeihyl-dibromoxyhydrouracil: 

CH3.N — CO 

I        I 
CO  CBr2 

I        I 
CH3.N— CHOH 


62  Researches    on   Pyrimidins 

This  pyrimidin  crystallized  from  bromine  water  in  micro- 
scopic prisms  with  curved  outline.  It  melted  at  135°  to  136° 
to  a  clear  oil.  Analysis  (Kjeldahl)  : 

Calculated  for 


Found: 
N  ................................        8.86  9.0 

/,  ^-Dimethyl-  ^-bromuracil: 

CH3N—  CO 

I        I 
CO    CBr 

I        II 
CH3N—  CH 

This  compound  was  prepared  by  digesting  the  above  hydro- 
uracil  derivative  with  absolute  alcohol.  It  was  purified  for 
analysis  by  recrystallization  from  water  and  melted  at  181°  to 
182°  to  a  clear  oil.  Analysis  (Kjeldahl)  : 

Calculated  for 
C6H7O2N2Br  :  Fou  nd  : 

N  ................................        12.79  13.0 

2-Oxy-  ^-methyl-  6-aminopyrimidin  (^-methylcytosin)  : 

N=C.NH2 

I      I 
CO  CH 

I       II 
CH3.N—  CH 

Six  and  eight-tenths  grams  of  anhydrous  cytosin  and  3.4 
grams  of  potassium  hydroxide  were  dissolved  in  60  cc.  of  boil- 
ing, absolute  alcohol,  and  16  grams  of  methyl  iodide  added  to 
the  solution.  After  boiling  for  two  hours  the  solution  was 
evaporated  to  dryness  and  the  residue  of  pyrimidin  and  potas- 
sium iodide  dissolved  in  cold  water.  The  iodine  was  removed 
with  silver  sulphate  and  the  excess  of  silver  by  precipitation  with 
hydrogen  sulphide.  The  sulphuric  acid  was  then  quantitatively 
removed  with  barium  hydroxide  and  the  filtrate  from  barium 
sulphate  concentrated  to  a  small  volume.  The  base  was  pre- 
cipitated from  this  solution  with  a  hot,  saturated  solution  of 
mercuric  chloride  and  the  mercury  precipitate  decomposed  in 


Treat  B.  Johnson  and  Samuel  H.  Clapp        63 

the  usual  way  with  hydrogen  sulphide;  the  chlorine  removed 
with  silver  sulphate,  the  excess  of  silver  with  hydrogen  sulphide, 
and  the  sulphuric  acid  with  barium  hydroxide.  When  this 
solution  was  evaporated  to  dryness  we  obtained  about  i .  i  gram 
of  the  pyrimidin  associated  with  a  small  amount  of  unaltered 
cytosin.  The  small  yield  is  partly  explained  by  the  fact  that  the 
base  volatilizes  with  aqueous  vapors.  It  was  purified  by  recrys- 
tallization  from  methylalcohol.  It  separated  in  beautiful, 
distinct  prisms  which  decomposed  at  about  278°  to  279°  to  a 
dark  oil.  This  decomposition  point  varies  according  to  the 
rate  of  heating.  The  base  was  extremely  soluble  in  water  and 
did  not  contain  water  of  crystallization.  Analysis  (Kjeldahl) : 

Calculated  for  Found: 

C5H7ON3:  I.  H. 

N 33.60  33.57     33.9 

The  chloroplatinate  of  ^-methylcytosin: 

Was  prepared  by  adding  a  solution  of  platinum  chloride  to  a 
hydrochloric  acid  solution  of  the  base.  It  crystallized  from 
water  in  long,  slender  prisms.  The  salt  contained  two  molecules 
of  water  of  crystallization  which  was  determined  by  heating  at 


I.  0 . 0513  gram  salt  lost  0. 0028  gram  H2O. 
II.  0.2103      "       "     "      0.0111    "       " 
III.  0.0841      "       "     "      0.0045    " 

Calculated  for  Found : 

(CsH7ON3.HCl)2.Pt  C14.2H2O:          I.  II.          III. 

H9O..  5.18  5.45     5.28     5.35 


Platinum  determination  in  anhydrous  salt : 

I.  0.04 78  gram  salt  gave  0.0142  gram  Pt. 
II.  0.1991      "       "     "        0.0591      " 
III.  0.0793      "       "     "        0.232 

Calculated  for  Found : 

(C5H7ON3.HCl)2.PtCl4:  I.  II.  III. 

Pt..  29.54  29.71     29.68     29.26 


Pier  ate  of  j-methylcytosin: 

This  salt  was  very  insoluble  in  cold  water,  and   crystallized 
from  hot  water  in  long  prisms.     The  decomposition  point  varies 


64  Researches    on   Pyrimidins 

greatly  according  to  the  rate  of  heating.     When  heated  slowly 
it  decomposed  at  about  280°  with  effervescence.     Analysis: 

0.1351  gram  substance  gave  28.7  cc.  N2  at  25°  and  770  mm. 

Calculated  for 
C5H7ON3.C6H3O7N3:  Found: 

N  ..............................  23.73  24.0 

$-M  ethyl-  5-bromuracil: 

NH—  CO 

I  I 

CO       CBr 

I  II 

CH8N  --  CH 

When  3-methylcytosin  was  dissolved  in  a  little  cold  water  and 
liquid  bromine  added  to  the  solution,  a  heavy  precipitate  was 
obtained.  This  dissolved  immediately,  on  warming,  and  after 
heating  about  ten  minutes  on  the  steambath,  the  solution  was 
evaporated  to  dryness  under  diminished  pressure.  The  -residue 
obtained  was  then  dissolved  in  a  small  amount  of  absolute 
alcohol  and  the  solution  boiled  for  five  hours.  On  cooling,  the 
brompyrimidin  separated  in  needles.  It  crystallized  from  hot 
water  in  long,  slender,  distorted  needles.  They  decomposed 
at  about  255°  to  260°  to  a  clear  oil  with  practically  no  effer- 
vescence. The  compound  was  soluble  in  cold,  dilute  sodium 
hydroxide  solution  and  was  precipitated  again  by  acetic  acid. 
It  gave  a  strong  test  for  bromine.  A  mixture  of  the  pyrimidin 
and  the  isomeric  i  -methyl-  5-bromuracil1  melted  at  175°  to 
195°.  A  mixture  of  the  pyrimidin  and  5-bromuracil  melted 
from  230°  to  270°.  It  did  not  contain  water  of  crystallization. 
Analysis  (Kjeldahl)  : 

Calculated  for  Found  : 

I.  II. 


N  ........................        13.66  13.53     13.68 

2-Oxy-  6-methylphenylamino  pyrimidin  : 

N—  C.N(CH8)  (C6HS) 

I  I 

CO       CH 

I  II 

NH—  CH 

1  Johnson  and  Heyl  :  Loc.  cit. 


Treat  B.  Johnson  and  Samuel  H.  Clapp         65 

Ten  grams  of  2-ethylmercapto-6-chlorpyrimidin  and  two 
molecular  proportions  of  monomethylaniline  (twelve  grams) 
were  dissolved  in  dry  benzene  and  the  solution  boiled  for  eight 
hours.  The  benzene  was  then  evaporated,  the  residue  dissolved 
in  ammonia  and  the  excess  of  monomethylaniline  removed  by 
distillation  with  steam.  When  this  solution  was  concentrated 
we  obtained  the  mercaptopyrimidin  as  an  oil  which  did  not 
solidify  on  standing.  The  crude  mercapto  derivative  was  con- 
verted into  the  oxygen  derivative  by  digesting  with  hydrobromic 
acid.  The  yield  was  80  per  cent  of  the  theoretical.  The  com- 
pound is  very  insoluble  in  water  and  chloroform  and  crystallizes 
from  alcohol  in  beautiful  hexagonal  tables  which  do  not  decom- 
pose below  285°.  Analysis  (Kjeldahl) : 

Calculated  for 
CnHuON3:    '  Found: 

N 20.90  20.71 

2-Oxy-  3-methyl-  6-methylphenylaminopyrimidin : 
N=CN(CH3)  (C6H6) 

I       I 
CO  CH 

I       II 
CH3N— CH 

Seven  and  five-tenths  grams  of  2-oxy-6-methylphenylamino- 
pyrimidin,  2.1  grams  of  potassium  hydroxide,  and  12  grams 
of  methyliodide  were  dissolved  in  150  cc.  of  absolute  alcohol 
and  the  solution  boiled  for  two  hours.  The  solution  was 
then  evaporated  to  dryness  and  the  residue  extracted  with 
chloroform.  When  the  chloroform  was  evaporated  we  obtained 
the  hydriodide  of  the  pyrimidin  base.  The  base  was  obtained 
by  decomposing  the  salt  with  sodium  hydroxide  and  weighed 
5.5  grams  or  69  per  cent  of  theoretical.  It  crystallized  from 
water  in  long,  striated  prisms  which  melted  sharply  at  186°  to 
187°  to  a  clear  oil  without  effervescence.  Analysis  (Kjeldahl): 

Calculated  for 

CuHuONjt:  Found: 

N 19.53  19.78 

2-Oxy-j , ^-dimethyl-  6-aminopyrimidin  (3 , $-Dimethyl-cytosiri)  : 

N=C.NH2 

I        I 
CO    CCH8 

I        II 
CH3.N— CH 


66  Researches    on   Pyrimidins 

5-Methylcytosin1  was  converted  into  this  base  by  alkylation 
with  potassium  hydroxide  and  methyliodide  in  the  usual  manner, 
and  the  new  pyrimidin  isolated  in  the  same  way  as  3-methyl- 
cytosin.  The  compound  was  extremely  soluble  in  water  and 
volatilized  with  aqueous  vapors.  It  separated  from  methyl- 
alcohol  in  prisms.  It  had  no  definite  melting  point,  but  decom- 
posed from  300°  to  310°,  according  to  the  rate  of  heating,  with 
effervescence.  Analysis  (Kjeldahl) : 

Calculated  for  Found; 

C6H9ONa:  I.  II. 

N 30.22  30.09     29.76 

Conversion  of  3,$-dimethylcytosin  into  ^-methylthymin: 
Some  3,5-dimethylcytosin  was  dissolved  in  strong  bromine 
water,  the  solution  warmed  on  the  steambath  for  ten  minutes, 
and  then  evaporated  to  dryness  in  a  vacuum.  We  obtained 
a  crystalline  deposit  which  was  digested  with  absolute  alcohol 
for  five  hours.  The  alcohol  was  then  removed  by  evaporation 
and  the  residue  redissolved  in  hot  water.  Needle-like  prisms 
separated,  on  cooling,  which  melted  at  160°  with  effervescence 
to  a  colorless  oil.  This  oil  immediately  solidified  on  cooling 
and  then  melted  at  280°  to  282°  to  an  oil  without  effervescence. 
They  did  not  contain  bromine  and  were  soluble  in  alkalies.  We 
did  not  obtain  enough  of  this  material  for  analysis  but  it  was 
probably  ^-methyluramino-a-methylacrylic  acid: 

NH2     COOH 

I 
CO      C.CH3 

I! 

CH,.N CH 

When  the  filtrate  (above)  was  concentrated  and  cooled  the 
characteristic  crystals  of  3 -methyl thymin  separated.  They  melted 
at  280°  to  282°  to  an  oil.  A  mixture  of  pure  3 -methyl thymin 
and  this  compound  melted  at  the  same  temperature.  Analysis 
(Kjeldahl) : 

Calculated  for 

C6H8O2N2:  Found; 

N..  20.00  20.3 


Wheeler  and  Johnson:  Amer.  Chem.  Journ.,  xxxi,  p.  591. 


Treat  B.  Johnson  and  Samuel  H.  Clapp         67 

CONDUCTIVITY  MEASUREMENTS  ON  THYMIN,  i-METHYL- 
THYMIN,  3-METHYLTHYMIN,  i,3-DIMETHYLTHYMIN  AND 
4-METHYLURACIL. 

BY  N.  A.   MARTIN. 

In  a  series  of  conductivity  measurements  on  thymin  and  its 
nitrogen-methyl  derivatives  it  was  found  that  the  conductivities 
of  thymin  and  1,3 -dimethyl thymin  remained  nearly  constant. 
The  very  slight  increase  in  conductivity  observed  was  probably 
due  to  small  amounts  of  impurities  absorbed  from  the  glass  and 
air.  The  conductivity  of  water  was  found  to  increase  at  about 
the  same  rate. 

On  the  other  hand,  duplicate  determinations  on  i -methyl  - 
thymin  and  3 -methyl thymin  did  not  give  agreeing  results  nor 
could  dissociation  constants  be  calculated.  The  investigation 
showed  that  the  conductivity  of  these  two  pyrimidins  rose  with 
the  length  of  time  they  were  kept  in  solution.  The  greatest 
rise  in  conductivity  was  observed  in  the  determinations  on  3- 
methyl  thymin. 

The  measurements  were  carried  out  by  the  customary  Kohl- 
rausch  method  in  a  thermostat  at  25°.  The  water  used  was 
redistilled  over  barium  hydroxide,  rejecting  all  that  gave  a  test 
for  ammonia  with  Nessler's  reagent,  until  it  had  a  specific  con- 
ductivity of  approximately  2  X  io~6,  and  the  conductivity 
vessel,  pipettes,  etc.,  were  thoroughly  steamed  before  using. 

The  rise  in  conductivity  was  determined  by  preparing  20  cc. 
of  exactly  -$-%  solution  of  the  substance  directly  in  the  vessel 
and  measuring  its  conductivity,  at  intervals,  until  it  remained 
practically  constant.  The  rise  in  specific  conductivity  of  pure 
water,  due  to  absorption  of  air,  solution  of  soda  from  the  walls 
of  the  vessel,  etc.,  was  also  determined  and  found  to  be  prac- 
tically zero  (o .  o72  per  hour) . 

In  calculating  results  the  amount  of  hydrolysis  could  not  be 
determined  as  the  amount  of  dissociation  of  the  resulting  ura- 
minoacrylic  acids  (?)  was  unknown.  The  specific  and  molec- 
ular conductivities  were  calculated  and  the  latter  plotted  as 
ordinates  with  the  time  in  hours  as  abscissas.  As  a  reference 
line  the  rise  in  conductivity  of  water  was  also  plotted,  using  64,000 
times  the  specific  conductivity  to  agree  with  the  molecular 
conductivity  of  the  solutions  (A  64  =  64,000  x). 


68 


Researches    on  Pyrimidins 


Molecular  conductivity  of  the  pyrimidins  in  ^  solution  at  25°,  showing  increase 
due  to  hydrolysis. 


Time. 

Thymin. 

1  ,3-Dimethly- 
thymin. 

l-Methylthymin. 

3-Methyl- 
thymin. 

4-Methyl- 
uracil. 

£  hour 

0.23 

0.35 

1      " 

0.75 

1 

0.37 

0.49 

0.38 

2       " 

(  +  i)  0.41 

(+i)1.04 

0.90 

3       " 

0.42 

1.17 

4 

0.44 

1.36 

5       " 

0.45 

1.54 

6       " 

0.46 

7 

0.47 

1.98 

8       " 

17       " 

0.68 

2.50 

18       " 

0.69 

2.53 

19£     " 

0.72 

2.67 

20       " 

0.74 

22 

(  +  })0.75 

4.51 

23       " 

(  +  i)  0.57 

4.67 

24       " 

0.57 

4.96 

8.90 

25 

26       " 

27       " 

5.28 

10.19 

28 

5.56 

30       " 

5.75 

41       " 

13.53 

49§     « 

2.97 

55i     " 

6.02 

Treat  B.  Johnson  and  Samuel  H.  Clapp         69 


Specific  conductivity  of 


pyrimidin  solutions  at  25°,  showing  increase  due 
to  hydrolysis. 


Time. 

H2O. 

Thymin. 

1,3-Di- 
methyl- 
thymm. 

l-Methyl- 
thymin. 

3-Methyl- 
thymin. 

4-Methyl- 
uracil. 

£  hour 

0.0521 

0.0536 

0.0655 

I        " 

0.0412 

1 

0.0522 

0.0857 

0.0577 

0.0660 

2 

0.0524 

(  +  $)0.0565 

(  +  $)0.04162 

0.0414 

3 

0.0626 

0.0566 

0.04182 

4 

0.0667 

0.04212 

5 

0.0569 

0.04240 

6 

0.0571 

7 

0.0672  + 

(  +  $)0.04308 

8 

0.0574 

17 

0.0555 

0.04107 

0.0439 

18 

0.04109 

0.0440 

19$      " 

0.0442 

20 

0.04113 

22 

0.04115 

0.04704 

23 

(  +  $)0.0589 

0.04116 

0.04730 

24 

0.04775 

0.03139 

25 

26 

0.0591 

27 

0.0592 

0.04824 

0.03159 

28 

0.0593 

0.04868 

30 

0.04898 

41 

0.03211 

49f      « 

0.0447 

55$      " 

0.04991 

Researches   on   Pyrimidins 


/r 


Wafer 


X.    RESEARCHES  ON  PYRIMIDINS:    THE   ACTION  OF 

DIAZOBENZENE  SULFONIC  ACID   ON  THYMIN, 

URACIL  AND  CYTOSIN. 

(Thirty-fourth  Paper.) 
BY  TREAT  B.  JOHNSON  AND  SAMUEL  H.  CLAPP. 

(From  the  Sheffield  Laboratory  of  Yale  University.} 
(Received  for  publication,  June  9,  1908.) 

We  have,  at  the  present  time,  practically  no  knowledge  of  the 
way  in  which  the  pyrimidins — thymin,  uracil  and  cytosin — are 
linked  in  the  nucleic  acid  molecule.  The  question  whether  they 
are  actually  as  such  contained  in  the  nucleic  acids,  from  which 
they  are  obtained,  has  not  been  settled.  The  recent  work  of 
Osborne  and  Heyl1  on  triticonucleic  acid,  and  of  Levene  and 
Mandel2  would  seem  to  indicate  that  they  do  not  result  from  the 
purin  bases,3  but  that  the  pyrimidin  nucleus  is  present  in  nucleic 
acids  in  the  simple  form. 

In  order  to  obtain  new  data,  which  might  prove  of  service  in 
settling  the  question  of  the  nature  of  the  linking  of  pyrimidins 
in  nucleic  acids,  we  undertook  this  investigation.  We  shall 
describe  the  behavior  of  diazobenzene  sulfonic  acid  on  thymin, 
uracil,  cytosin  and  some  of  their  alkyl  derivatives.4  A  sum- 
mary of  the  results  of  our  experiments,  and  their  significance,  is 
given  at  the  end  of  this  paper. 

Burian5  has  investigated  the  action  of  diazobenzene  sulfonic 
acid  on  several  nucleic  acids  and  purins.  He  examined  the 
nucleic  acids  from  sperma,  thymus,  yeast  and  spermatozoa  of  the 

1  Amer.  Journ.  of  Physiol.,  xxi,  p.  157. 

2  Biochem.  Zeitschr.,  ix,  p.  233. 

3  Asher-Spiro:    Ergeb.  d.  Physiol.,  v,  p.  795,  1905;    Burian:  Zeitschr.  f. 
physiol.  Chew.,  li,  p.   438,  1907. 

4  Johnson  and  Clapp:  This  Journal,  v,  p.  49. 

5  Ber.  d.  deutsch.  diem.  Gesellsch.,  xxxvii,  p.   708;   Zeitschr.  f.  physiol. 
Chem.,  li,  p.  435. 

163 


164  Researches  on   Pyrimidins 

herring;  and  states  that  they  do  not  react  with  this  reagent.  He 
showed,  on  the  other  hand,  that  the  purins — xanthin,  hypoxan- 
thin,  guanin,  adenin  and  theophyllin — in  which  the  hydrogen  in 
position  7  is  unsubstituted,  react  with  diazobenzene  sulfonic 
acid,  in  presence  of  alkali,  giving  intensely  colored  compounds. 
He  regards  the  compounds  formed  as  diazoamino  derivatives  of 
the  general  formula  I.  Substitution  in  the  pyrimidin  (alloxan) 


2C          sc  -  N  -  N  :  NC6H4S03H 

I  I          >C8 

3N *C  -N 

9 
I 

ring  apparently  had  no  influence  on  the  reaction.  On  the  other 
hand,  he  observed  that  purins  substituted  in  position  7 — theo- 
bromin,  caffein — and  also  uric  acid,  do  not  react  with  the  diazo 
acid.  Burian  concludes  from  these  results  that  the  xanthin 
bases  are  linked  in  the  nucleic  acids  at  the  nitrogen  atom  in  posi- 
tion 7. 

So  far  as  the  writers  are  aware  Evans1  was  the  first  investi- 
gator to  observe  that  a  diazobenzene  derivative  reacts  with  a 
pyrimidin  giving  a  colored  compound.  He  found,  for  example, 
that  2-oxy-4,6-dimethylpyrimidin,  II, 


CO        CH 

I  II 

NH CCH3 

II 

combines  with  diazobenzene  chloride,  in  presence  of  alkali,  giv- 
ing a  red  compound.  He  says:  "Es  ist  dies  ein  sehr  kraftiger 
Farbstoff. "  The  compound  was  unstable  and  no  formula  was 
assigned  it. 

Steudel2  afterwards  observed  that  natural  thymin  reacts  with 
diazobenzene  sulfonic  acid,  in  alkaline  solutions,  giving  an  intense 

1  Journ.  f.  prakt.  Ghent.,  xlviii,  p.  489. 

2  Zeitschr.  f.  physiol.  Chem.,  xlii,  p.  170. 


Treat  B.  Johnson  and  Samuel   H.  Clapp       165 

red  color.  Pauly  also  mentions  this  diazo  reaction  in  a  later 
publication1  and  states  that  it  cannot  be  used  to  distinguish 
between  the  pyrimidin  and  imidazol  rings.  He  observed,  for 
example,  that  4-methyluracil  gives  as  intense  a  color  with  diazo- 
benzene  sulfonic  acid  as  histidin. 

We  now  find  that  not  only  thymin  and  4-methyluracil,  but 
also  uracil,  4,5-dimethyluracil,  cytosin,  5-methylcytosin  and  5- 
bromuracil  react  under  proper  conditions  with  diazobenzene  sul- 
fonic acid  giving  red  colored  solutions.  The  colors  obtained  with 
thymin,  4-methyluracil,  4,5-dimethyluracil  and  5-methylcytosin 
are  much  more  intense  thant  those  obtained  with  uracil,  cytosin 
and  5-bromuracil.  Apparently,  the  character  of  the  groups 
occupying  the  4  and  5  positions  has  a  decided  influence  on  the 
intensity  of  the  color. 

We  have  also  made  the  interesting  observation  that  the  forma- 
tion of  red  colors  is  entirely  inhibited  by  substitution  in  the  3 
positions  of  the  uracil,  cytosin  and  thymin  molecules.  The 
assumption  that  the  diazo  compound  might  react  at  the  4  posi- 
tion of  the  pyrimidin  ring2  giving  azo  derivatives  is  excluded  by 
Pauly's  observation3  and  also  by  the  fact  that  4,  5-dimethyluracil 
reacts  with  the  diazo  acid  giving  a  red  color.  Substitution  in 
position  i  of  thymin  does  not  prevent  the  formation  of  a  red  color, 
i -Methyl thymin,4  for  example,  gave  as  intense  a  color  as  thymin 
itself.  On  the  other  hand  a  red  color  was  not  obtained  with  the 
diazo  acid  when  the  hydrogens  in  positions  i  and  3  or  3  alone  of 
thymin  were  substituted  by  methyl  groups. 

Similar  observations  were  also  made  in  the  cases  of  uracil  and 
5-bromuracil.  While  these  pyrimidins  gave  red  colors  with  the 
diazo  acid,  no  colors  were  obtained  when  i,3-dimethyluracil5 
and  3 -methyl- 5-bromuracil  were  tested  with  the  reagent.  The 
corresponding  3-methyluracil  is  unknown.  The  formation  of  a 
color  in  the  cases  of  cytosin,  III,  and  5-methylcytosin,  VI,  is  not 
dependent  upon  the  presence  of  the  free  amino  radical.  2-Oxy- 

1  Zeitschr.  f.  physiol.  Chem.,  xlii,  p.  512. 

2Burian:  Zeitschr.  f.  physiol.  Chem.,  xlii,  p.  297;  Mann's  Chemistry  of 
the  Proteids,  p.  431,  1906. 

3  Loc.  cit. 

4  Johnson  and  Clapp :  Loc.  cit. 

5  Ibid. 


1 66  Researches  on   Pyrimidins 

6-methylphenylaminopyrimidin  V,1  gave  as  intense  a  color  as 
cytosin,  III,  while,  on  the  other  hand,  no  color  was  obtained  with 
3-methylcytosin,  IV,  3, 5-dimethylcytosin,  VII,  and  2-0x7-3- 
methyl-6-methylphenylamino-pyrimidin,  VIII. 


CN  (CH3)  (C6H5) 
CH 


N  =    =  CNH2  N  =  CNH2  N  CN  (CH3)  (C6H5) 

1  I 

CO          CCH3          CO        CCH3 

I              II                   I  II 

NH  -  CH       CH3N CH 

VI  VII  VIII 

The  remarkable  tendency  of  certain  pyrimidins  to  react  with 
diazobenzene  sulfonic  acid,  and  the  apparent  inertness  of  the 
same  ring  in  purins  are  of  especial  interest.  According  to  Bu- 
rian2  substitution  in  the  pyrimidin  nucleus  of  purins  did  not  influ- 
ence the  reaction  with  the  diazo  acid.  While  purins  are  closely 
related  in  structure  to  pyrimidins  it  is  important  to  point  out 
in  this  connection  that  positions  i  and  3  of  the  pyrimidin  ring 
do  not  necessarily  correspond  to  positions  i  and  3  in  purins. 
While  the  pyrimidin  nucleus  is  symmetrical,  the  purin,  on  the 
other  hand,  is  unsymmetrical  with  respect  to  the  2  position. 
Two  purins  can  theoretically  be  formed  from  a  pyrimidin  ring 
according  as  the  glyoxalin  ring  is  joined  at  the  4,  5  or  5,6  posi- 
tions. An  inspection  of  the  formulas  below  will  show  that  this 
involves  a  change  in  the  numbering  of  the  atoms  in  the  pyri- 
midin nucleus. 


c  N. 


2C          5C-N7  C          C 

I         I      >c-  || 

SN C-N  N C 

4          9 

Purin.  Pyrimidin. 

1  Johnson  and  Clapp :  Loc.  cit. 

2  Loc.  cit. 


Treat  B.  Johnson  and  Samuel  H.  Clapp       167 

It  is  also  of  interest  to  note  here  that  6-oxypyrimidin1  and 
6-aminopyrimidin?  do  not  give  a  red  color  with  diazobenzene 
sulfonic  acid.  Whether  this  reagent  reacts  to  form  colored  com- 
pounds only  with  pyrimidins  having  a  — CO-NH —  grouping  in 
the  i,  2  or  2,  3  positions  must  be  decided  by  further  experi- 
ments. 

The  compounds  formed  by  the  action  of  diazobenzene  sul- 
fonic acid  or  pyrimidins  appear  to  be  more  unstable  than  those 
formed  in  the  case  of  purins.  Two  attempts  to  isolate  the  reac- 
tion-product in  the  case  of  thymin  were  unsuccessful. 

The  diazo  acid  used  in  our  work  was  prepared  according  to  the 
directions  of  Pauly.3  That  the  test  shall  not  be  found  to  be 
capricious  it  is  absolutely  necessary  that  the  acid  be  pure  and 
freshly  prepared. 

METHODS    OF    APPLYING    THE    TEST. 

/.     With  jo  per  cent  sodium  hydroxide  solution. 

Five  to  ten  milligrams  of  the  pyrimidin  are  dissolved  in  0.5  cc. 
of  10  per  cent  sodium  hydroxide  solution  and  about  5.0  milli- 
grams of  diazobenzene  sulfonic  acid  then  added  to  the  solution. 
If  no  reaction  takes  place  the  solution  usually  assumes  a  yellow 
or  orange  color.  When  a  red  color  is  formed  it  usually  develops 
quite  rapidly.  The  red  color  is  usually  quite  permanent,  lasting 
in  some  cases  (thymin)  for  several  hours. 

2.     With  ^  sodium  hydroxide  solution. 

Dissolve  5.0  to  10.0  milligrams  of  the  pyrimidin  in  2  cc.  of 
*-Q  sodium  hydroxide  solution  and  add  5.0  to  10.0  milligrams  of 
the  sulfonic  acid.  This  method  of  testing  is  not  as  reliable  as 
Method  i. 

3.     Testing  on  a  watch  glass. 

Five  to  ten  milligrams  of  the  pyrimidin  and  an  equal  weight 
of  the  sulfonic  acid  are  mixed  together,  with  a  glass  rod,  on  a  dry 

1  Wheeler:  This  Journal,  iii,  p.  285,  1907. 

2  Biittner :  Ber.  d.  deutsch.  chem.  Gesellsch.,  xxxvi,  p.  2232,  1903 :  Wheeler: 
Loc.  cit. 

3  Zeitschr.  f.  physiol.  Chem.,  xlii,  p.  516. 


1 68 


Researches  on  Pyrimidins 


watch  glass.  A  drop  of  10  per  cent  sodium  hydroxide  solution 
is  then  allowed  to  flow  into  the  mixture.  The  red  color  develops 
immediately  under  these  conditions.  This  method  of  applying 
the  diazo  test  is  recommended  on  account  of  its  delicacy  and 
reliability. 

The  results  of  our  experiments  are  given,  for  comparison,  in  the 
following  tables : 


TABLE    I. 


Pyrimidins. 

0.5  ce.  10  per  cent 
NaOH  solution. 

2.0  cc.  T^  NaOH 
solution. 

Test  on  watch- 
glass. 

NH             PO 

Intense  red  color, 
which  disappears 
on  diluting  with 
water. 

Light  red  which 
fades  rapidly. 

Intense  red  color. 

1                    1 

CO           CCH3 

1          1! 

NH           PH 

(Thymin). 

PH  N           PO 

Intense  red  color, 
which  disappears 
on  diluting  with 
water. 

No  color.* 

Intense  red  color. 

1              1 
CO        CCH3 

1             II 
NH  CH 
(1-Methylthymin.) 

NH            PO 

No  color. 

No  color. 

No  color. 

1 
CO         CCH3 

1             II 

PH  N            PH 

(3-Methylthymin.) 

PH  N            PO 

No  color. 

No  color. 

No  color. 

CO      CCH3 

1           II 
PH  N           PH 

(1,  3-Dimethylthy- 
min.) 

*Note — The  statement — no  color — indicates  that  no  red  color  was  formed. 


Treat  B.  Johnson  and  Samuel  H.  Clapp       169 


TABLE    II. 


Pyrimidins. 

0.5  cc.  10  per  cent 
NaOH  solution. 

2.0  cc.    N^NaOH 
solution. 

Test  on  watch- 
glass. 

NH  CO 

1               1 
CO           CH 

1               II 

T\ITJ                      pTT 

Red  color  but  not 

as  intense  as  with 
thymin. 

Red    color    which 
developed  slowly. 
Color  permanent 

Red  color. 

(Uracil.) 

PTT  1ST                PO 

Red  color. 

Red  color. 

Red  color. 

CO          CH 

II 

ATTT                      pTT 

(1-Methyluracil). 
NH  CO 

1         ! 

CO       CH 

1           II 
PH  N            PTT 

(3-Methyluracil) 

CH3N  CO 

i 
CO       CH 

CR  AT            PTT 

No  color. 

No  color. 

No  color. 

(1,  3-Dimethyluracil) 

1 7o 


Researches  on   Pyrimidins 


TABLE    III. 


Pyrimidins. 

0.5  cc.  10  per  cant 
NaOH  solution. 

2.0  cc.  ^NaOH 
solution, 

Test  on  watch- 
glass. 

NTT             TO 

I                     I 
CO           CBr 

1                 II 

Red  color. 

Faint    red    color 
which   develops 

Faint   red    color. 

!                    11 
NTT            PH 

slowly. 

(5-Bromuracil.) 

flTT   AT                        pf) 

|                                                         1 

CO          CBr 

1              II 

Red  color. 

NTT            PTT 

(l-Methyl-5-brom- 

uracil.) 

NH  CO 

I 

CO       CBr 

II 

No  color. 

No  color. 

No  color. 

CH3N  CH 

(3-Methyl-5-brom- 

uracil). 

CH3N  CO 

1             1 

CO        CBr 

II 

No  color. 

No  color. 

No  color. 

CH3N  CH 

(1,  3-Dimethyl- 

..'•: 

5-bromuracil.) 

Treat  B.  Johnson  and  Samuel  H.  Clapp       171 


TABLE    IV. 


Pyrimidins. 

0.5cc.  10  per  cent 
NaOH  solution. 

2.0  cc.^  NaOH 
solution. 

Test  on  watch- 
glass. 

N  =  C.NH2 

1         1 

1         1 
CO     CH.H2O 

II 

Red    color    which 
developed  slowly. 

Faint  red. 

Red  color  like 
uracil. 

NH  —  CH 

(Cytosin.) 

N  =  CNH2 

CO    CH 

No  color. 

No  color. 

No  color. 

CH3N  —  CH 

(3-Methyl-cytosin)  . 

N  —  C 

/CH3 
»ji/ 

CO    CH 

ii 

Red  color. 

No  color. 

Red  color. 

II 
NH  —  CH 

CO     ( 

^CA 

3H 

t 

No  color. 

No  color. 

No  color. 

1 
CH8N  —  CH 

172 


Researches  on  Pyrimidins 


TABLE    V. 


Pyrimidins. 

0.5  cc.  10  per  cent 
NaOH  solution. 

2.0cc.yNffNaOH 
solution. 

Test  on  watch- 
glass. 

N  =  CNH2 

CO    C 

;CH3 

Intense  red  color. 

Faint  red  which 

Intense  red. 

1 

faded. 

NH  —  CH 

(5-Methyl-cytosin 

N  =  CNH2 

CO    C 

II 

CH3 

No  color. 

No  color. 

No  color. 

CH3N  —  CH 

(3,  5-Dimethyl- 

cytosin.) 

SUMMARY. 

(1)  Thymin,  uracil  and  cytosin  react  with  diazobenzene  sul- 
fonic  acid,  in  presence  of  alkali,  giving  red  colored  solutions. 

(2)  The  color  is  given  by  thymin  with  greater  intensity  than 
by  uracil  and  cytosin. 

(3)  Substitution  in  position  3  of  the  pyrimidin  ring  prevents 
the  formation  of  a  red  color. 

(4)  Accepting  the  statement  of    Burian,1  that  nucleic  acids 
do  not  react  with  diazobenzene  sulfonic  acid,  the  foregoing  ob- 
servations seem  to  indicate  that  thymin  and   probably  uracil 
and  cytosin  as  well  are  linked  in  nucleic  acids  at  position  3 . 

N CO 


CO       C 


(3)  N- 


(5)  Whether  the  pyrimidins  are  linked  to  phosphorus,  a  car- 
bohydrate complex  or  otherwise  must  be  decided  by  further 
study. 


Ber.  d.  deutsch.  chem.  Gesellsch,,  xxxvii,    p.    708;    Zeitschr.   f.   physiol. 
Chem,,  li,  p.  435. 


[Reprinted  from  the  American  Chemical  Journal,  Vol.  XI,. 
No.  2.    August,  1908.] 


[Contributions  from  the  Sheffield  Laboratory  of  Yale  University.] 

CLVIL— RESEARCHES  ON   PYRIMIDINES:      THE  AC- 
TION   OF    POTASSIUM   THIOCYANATE   UPON 
SOME  IMIDECHLORIDES. 
[THIRTY-FIFTH  PAPER.] 

By  TREAT  B.  JOHNSON  AND  WALTER  F.  STOREY. 

Two  papers  entitled  "The  Action  of  Potassium  Thiocyan- 
ate  upon  Imidechlorides"  have  previously  been  published 
from  this  laboratory. 

In  the  first  paper1  the  authors  showed  that  the  three  imide- 
chlorides,  viz.,  2-ethylmercapto-6-chlorpyrimidine,  I.,  2-ethyl- 
mercapto-5-methyl-6-chlorpyrimidine,  II.,  and  2-ethylmer- 

ipto-5-brom-6-chlorpyrimidine,  III.,  reacted  with  potassium 
thiocyanate,  under  certain  conditions,  giving  isothiocyanates. 

icy  made  no  attempts  to  obtain  evidence  of  the  interme- 
liate  formation  of  thiocyanates. 

N=CC1  N  =  CC1  N  — CC1 

II  II  II 

C2H5SC     CH        C,H5SC      CCH3      C2H6SC       CBr. 

'  II       II  II        II  II        II 

N  — CH  N  — CH  N— CH 

I.  II.  III. 

1  Wheeler  and  Bristol:  THIS  JOURNAL,  33,  448. 


132  Johnson  and  Storey. 

In  the  second  paper,1  Johnson  and  McCollum  described  an 
unique  case  of  the  molecular  rearrangement  of  a  thiocyanate 
into  an  isothiocyanate.  They  observed  that  2-ethylmercapto- 
5-ethoxy-6-chlorpyrimidine,  IV.,  reacted,  in  alcohol,  with 
potassium  thiocyanate,  giving  2-ethylmercapto-5-ethoxy-6- 
thiocyanpyrimidine,  V.,  which  then  underwent  a  metameric 
change  into  2-ethylmercapto-5-ethoxy-6-isothiocyanpyrimi- 
dine,  VI. 

N  =  CC1  N  =  CSCN  N  =  CNCS 

I  I  II  I         I 
C,H5SC      COC2H5        C,H5SC       COC2H5     C2H6SC       COC,H5. 

II  I!  II       II  II      II 

N  — CH  N  — CH  N  — CH 

IV.  V.  VI. 

The  work  described  in  this  paper  was  undertaken  with  the 
object  of  examining  the  behavior  of  potassium  thiocyanate 
towards  the  three  cyclic  imidechlorides,  viz.,  2-paratoluidino- 
6-chlorpyrimidine,  VII.,  2-orthotoluidmo-6-chlorpyrimidine, 
VIII.,  and  2-paratolyl-4-methyl-6-chlorpyrimidine,  IX.  In- 
cidentally we  have  also  reinvestigated  the  action  of  potassium 
thiocyanate  on  the  imidechlorides,  I.,  II.,  and  III.,  studied 
by  Wheeler  and  Bristol. 

N  =  CC1  N  =  CC1 

II  II 

/>-CH,.C6H,NHC      CH  o-CH3.C6H4NHC      CH 

II        II  II        II 

N  — CH  N  — CH 

VII.  VIII. 

N  =  CC1 

I  I 
4C       CH. 

II  II 
N— CCH3 

IX. 

2-Paratoluidino-6-chlorpyrimidine,  VII.,  and  2-orthotolui- 
dino-6-chlorpyrimidine,  VIII.,  were  prepared  from  2-ethyl- 
mercapto-6-oxypyrimidine.  This  mercaptopyrimidine  reacted, 
in  a  smooth  manner,  with  para-  and  orthotolmdine,  at  100°, 
giving  quantitative  yields  of  2-paratoluidino-6-oxypyrimidine 

1  THIS  JOURNAL,  36,  136. 


Researches  on  Pyrimidines. 


133 


and  2-orthotoluidino-6-oxypyrimidine,  respectively.  The  oxy- 
pyrimidines  were  then  converted  into  the  imidechlorides, 
VII.  and  VIII.,  by  treatment  with  phosphorus  oxychloride  or 
phosphorus  pentachloride.  These  two  chlorides  are  more 
stable  in  alcoholic  solutions  than  the  corresponding  2-ethyl- 
mercapto-6-chlorpyrimidine.  While  the  mercapto  deriva- 
tive is  decomposed  by  boiling  alcohol  the  toluidinopyrimi- 
dines  can  be  recrystallized  repeatedly  from  this  solvent  with- 
out alteration.  We  now  find  that  these  two  chlorides  do  not 
react  with  potassium  thiocyanate  under  normal  conditions. 
They  were  recovered  unaltered  after  digesting,  in  alcohol  or 
acetone,  with  potassium  thiocyanate  for  several  hours. 

On  the  other  hand,  2-paratolyl-4-methyl-6-chlorpyrimidine, 
IX.,  which  was  obtained  from  2-paratolyl-4-methyl-6-oxy- 
pyrimidine1  by  the  action  of  phosphorus  pentachloride,  re- 
acted in  a  smooth  manner  with  potassium  thiocyanate,  giv- 
ing a  good  yield  of  2-paratolyl-4-methyl-6-thiocyanpyrimi- 
dine,  X.  This  thiocyanate  was  stable  at  ordinary  tempera- 
ture and  reacted  with  thiobenzoic  acid,  giving  a  quantitative 
yield  of  2-paratolyl-4-methyl-6-thiopyrimidine.  When  heated 
above  its  melting  point,  the  thiocyanate  was  converted  into 
a  mixture  of  the  isothiocyanate,  XI.,  and  apparently  a  poly- 
meric form  of  the  isothiocyanate  melting  at  204°.  The  iso- 
thiocyanate reacted  with  aqueous  ammonia  at  ordinary  tem- 
perature, giving  2-paratolyl-4-methyl-6-thioureapyrimidine, 
XII. 

N  =  CSCN  N  =  CNCS 

II  II 

/>-CH3C6H4C      CH  />-CH8CflH4C       CH 


N— CCHS 
x. 


N  — CCH3 
XI. 


N  =  CNHCSNH2 

I  I 
/>-CH3C6H4C  —  CH. 

II  II 

N  —  CCH, 

XII. 


1  Clock:  Ber.  d.  chem.  Ges.,  21,  2658. 


134  Johnson  and  Storey. 

Wheeler  and  Bristol,1  in  their  investigation  of  the  action  of 
potassium  thiocyanate  on  the  imidechlorides,  2-ethylmer- 
capto-6-chlorpyrimidine,  I.,  2-ethylmercapto-5-methyl-6- 
chlorpyrimidine,  II.,  and  2-ethylmercapto-5-brom-6-chlor- 
pyrimidine,  III.,  worked  with  the  object  of  converting  these 
chlorides  into  isothiocyanates.  They  invariably  digested 
the  chlorides  with  potassium  thiocyanate  in  toluene  or  alco- 
hol for  3  to  15  hours.  Under  these  conditions  the  thiocyanates, 
if  formed,  would  be  converted  completely  into  isothiocyanates. 
We  now  find  that  these  imidechlorides  give  practically  quan- 
titative yields  of  the  thiocyanates  XIII.,  XIV.,  and  XV., 
when  warmed  in  alcohol  with  potassium  thiocyanate,  if  the 
time  of  digestion  is  limited  to  20  to  60  minutes.  The  thio- 
cyanates are  stable  at  ordinary  temperature  and  can  be  re- 
crystallized  from  alcohol  without  alteration.  They  rearrange 
smoothly  into  isothiocyanates  when  heated  above  their  melting 
points  or  when  digested  for  long  periods  with  alcohol.  The 
isothiocyanates,  when  formed  under  the  latter  condition,  re- 
act with  the  alcohol,  giving  the  corresponding  6-thiourethane- 
py  rimidines : 

N  =  CSCN  N  =  CSCN  N  =  CSCN 

II  II  II 

C2H5SC      CH  C2H6SC       CCH3  C2H5SC      CBr. 

II        II  II        II  II        II 

N  —  CH  N  —  CH  N  —  CH 

XIII.  XIV.  XV. 

The  melting  points  and  boiling  points  of  all  the  6-thio- 
cyanpyrimidines,  6-isothiocyanpyrimidines,  and  corresponding 
6-thioureapyrimidines,  which  have  been  prepared  in  this  lab- 
oratory, are  given  in  the  following  table : 

1  Loc.  cit. 


„  .  «  - 


Iff 

lii? 


Researches  on  Pyrimidines. 

P  P  P 


B  • 


0=0 — o  ^Oo=ri- 

w  w  q-°w  o 


135 


sfe 


O 


tn 


o  O 


O 
~ 


P 

W 


00 


P 

-.  w 

-B-as 


o 
Jz; 

N»X 


oo  ^CO 

•°o 


z! 


3 


P 
W 
^ 


S 


p 

1 
w 
§ 


136  Johnson  and  Storey. 


P!  i  if H 

I  B  I  W  ?°g==g— gl 

1^8=8-8         * 

s     o  c  >      "      w  o 

"     s°  ^        i 

3*hH  W 

S  M  0-=  -3 


B»To 


o 


o 


K&  "  ° 

Q^  ^2 


O  ^H  flL 

'5  a 


v; 


3  5  *&| 

M                     O  O  ^Cn    ^  B* 

||     ?!  -°|  I 

w             ^"W  "W  5- 

P  =L  » >s  ^ 


a 


oCO  ^ 

*       /""N*  W 

Ca    H^ 

O    •<  g' 

^  .? 
P 

P!  I 


Researches  on  Pyrimi  dines. 
EXPERIMENTAL   PART. 


137 

=  CSCN 


2-Ethylmercapto-6-thiocyanpyrimidine,       C2H5S.C       CH    . 


N— CH 


By  DR.  E.  V.  MCCOLLUM. 


Three  and  nine-tenths  grams  of  potassium  thiocyanate 
were  dissolved  in  40  cc.  of  95  per  cent  alcohol  and  7  grams 
of  2-ethylmercapto-6-chlorpyrimidine  added  to  the  solu- 
tion. There  was  an  immediate  reaction  with  separa- 
tion of  potassium  chloride.  The  mixture  was  warmed 
on  the  steam  bath  for  twenty  minutes  and  the  insolu- 
ble potassium  chloride  separated  by  nitration.  On  cooling  the 
alcohol  solution,  the  thiocyanate  deposited  in  prismatic  crystals 
which  were  purified  for  analysis  by  recrystallization  from 
alcohol.  It  separated  in  aggregates  of  rectangular  prisms 
melting  without  effervescence  at  82°  to  a  clear  oil.  The  com- 
pound was  insoluble  in  alkali  and  did  not  react  with  ammonia 
or  aniline  at  100°.  Analysis  (Kjeldahl) : 


Calculated  for  CT^NS^.  I. 

N  21.31  20.89 


Pound. 
II. 

21.32 


III. 
2I.O9 


When  the  alcohol  filtrates  were  combined  and  evaporated 
to  dryness  a  yellow,  crystalline  residue  was  obtained  which 
partially  dissolved  in  cold  10  per  cent  solution  of  sodium 
hydroxide.  When  this  solution  was  acidified  with  acetic  acid 
we  obtained  0.3  gram  of  material  which  crystallized  from 
alcohol  in  flat  prisms  or  plates  melting  at92°-93°.  The  com- 
pound was  identical  with  the  2-ethylmercapto-6-thionethylure- 
thanepyrimidine  described  by  Wheeler  and  Bristol.1  A  quan- 
titative yield  of  the  above  thiocyanate  can  be  obtained 
by  boiling  2-ethylmercapto-6-chlorpyrimidine  in  acetone  solu- 
tion with  potassium  thiocyanate.  It  was  very  soluble  in  ace- 
tone and  separated  in  prismatic  crystals  melting  at  8i°-82°. 

1  Loc.  cit. 


138  Johnson  and  Storey. 

N=C.NCS 

2-Ethylmercapto-6-isothiocyanpyrimidine,   C2H5SC    CH 

II      II 
N— CH 

BY  DR.  E.  V.  MCCOLLUM. 

2-Ethylmercapto-6-thiocyanpyrimidine  shows  no  tendency 
to  rearrange  to  the  isothiocyanate  at  ordinary  temperature. 
On  the  other  hand,  a  rearrangement  took  place  when  the 
thiocyanate  was  heated  for  4  to  5  hours  at  8o°-9O°.  The 
isothiocyanate  was  obtained  as  an  oil  which  reacted  at  once 
with  aniline,  giving  2-ethylmercapto-6-phenylthioureapyrimi- 
dine1  melting  at  205°. 

The  isothiocyanate  was  obtained  as  a  yellow  oil  boiling  at 
200°-205°  (45-50  mm.)  when  the  thiocyanate  was  distilled. 
It  did  not  crystallize  on  standing  but  a  yellow,  crystalline 
compound  slowly  deposited.  This  was  difficultly  soluble  in 
benzene  and  practically  insoluble  in  alcohol.  It  melted  at 
i75°-i77°  and  did  not  react  with  ammonia.  The  compound 
is  apparently  identical  with  the  product  which  Wheeler  and 
Bristol  obtained  by  treating  2-ethylmercapto-6-chlorpyrimi- 
dine  with  potassium  thiocyanate.  It  is  probably  a  polymeric 
form  of  the  isothiocyanate,  (CyHyNgS^. 

The  isothiocyanate  reacted  at  once  with  aqueous  ammonia, 
with  evolution  of  heat,  giving  2-ethylmercapto-6-thiourea- 
pyrimidine2  melting  at  214°. 

2-Ethylmercapto-5-methyl-6-thiocyanpyrimidine, 
N^C.SCN 

I  I 

C2H5SC    CCH3.— Five    grams    of     2-ethylmercapto-5-methyl- 

II  II 
N— CH 

6-chlorpyrimidine  and  3.5  grams  of  dry  potassium  thiocyanate 
were  dissolved  in  25  cc.  of  absolute  alcohol  and  the  solution 
boiled  for  i  hour.  The  undissolved  potassium  chloride  was 
then  filtered  off  and  the  solution  evaporated  on  the  steam 
bath.  We  obtained  a  syrup  which  was  triturated  with  cold 
water  to  remove  any  potassium  chloride  and  then  extracted 

1  Wheeler  and  Bristol:  Loc.  cit. 


Researches  on  Pyrimidines.  139 

with  ether.  When  the  ether  was  evaporated  we  obtained  an 
oil  which  did  not  solidify  after  standing  for  several  days.  This 
oil  partially  dissolved  in  10  per  cent  sodium  hydroxide.  The 
insoluble  portion  solidified  on  standing,  and  crystallized  from 
95  per  cent  alcohol  in  beautiful  prisms  melting  without  effer- 
vescence at  95°  to  a  clear  oil.  It  did  not  react  with  ammonia 
or  aniline  and  a  nitrogen  determination  agreed  with  the  cal- 
culated value  for  a  thiocyanate  (Kjeldahl) : 

Calculated  for  C8H9N8Sj.  Found. 

N  19-90  19.6 

The  thiocyanate  dissolved  at  once  in  cold  thioacetic  acid 
without  apparent  evolution  of  heat.  On  standing,  beautiful 
prismatic  crystals  deposited  which  melted  at  i79°-i8o°.  This 
compound  was  not  examined  further  but  it  probably  was 
2-ethylmercapto-5-methyl-6-thiopyrimidine.  It  dissolved  in  al- 
kalis and  gave  a  test  for  sulphur. 

When  the  sodium  hydroxide  solution  (above)  was  acidified 
with  acetic  acid  we  obtained  an  oil  which  soon  solidified.  It 
was  insoluble  in  water  but  crystallized  from  95  per  cent  alcohol 
in  stout  prisms  melting  at  90°.  It  was  identical  with  2-ethyl- 
mercapto-j-methyl-d-thionurethanepyrimidine, 
N=C.NHCSOC2H5 

C2H5SC     CCH3  ,  which  was  described  by  Wheeler 

II      II 
N— CH 

and  Bristol.1  A  mixture  of  the  two  compounds  melted  at 
89°-9o0. 

2-Ethylmercapto-5-brom-6-thiocyanpyrimidine, 
N  =  CSCN 

.1     I 

C2H5S.C       CBr. — This    thiocyanate    was    prepared    in    the 

II        II 
N  — CH 

following  manner:  Five  grams  of  2-ethylmercapto-5-brom-6- 
chlorpyrimidine  and  2.5  grams  of  potassium  thiocyanate  were 
dissolved  in  50  cc.  of  95  per  cent  alcohol  and  the  solution  boiled 
on  the  steam  bath  for  20  minutes.  The  insoluble  potassium 

1  Loc.  cit. 


140  Johnson  and  Storey. 

chloride  was  filtered  off  and  the  filtrate  cooled,  when  the 
thiocyanate  deposited  in  prisms  melting  at  8 1°-82°.  They 
were  very  soluble  in  acetone,  boiling  ligroin,  warm  alcohol, 
and  benzene.  The  compound  did  not  dissolve  in  sodium 
hydroxide  and  could  be  warmed  with  ammonia  without  altera- 
tion. Analysis  (Kjeldahl) : 

Found. 
Calculated  for  C7H6N3S2Br.  I.  II. 

N  15.21  15.32  15.28 

Action  of  Thioacetic  And  Thiobenzoic  Acids  On  2-Ethyl- 
mercapto-^-brom-6-thiocyanpyrimidine: — About  0.3  gram  of  the 
thiocyanate  was  dissolved  in  a  small  quantity  of  thioacetic 
acid.  Reaction  took  place  at  once,  on  warming,  without 
evolution  of  carbon  bisulphide,  giving  large,  well-developed 
prisms.  The  compound  crystallized  from  benzene  in  rhombic 
prisms  that  melted  at  198°  with  slight  effervescence.  It 
was  identified  as  2-ethylmercapto-5-brom-6-thiopyrimidine.1 
A  mixture  of  the  two  products  melted  at  the  same  temperature. 
The  same  6-thiopyrimidine  was  obtained  when  the  thiocyanate 
was  warmed  in  a  water  bath  with  a  molecular  proportion  of 
thiobenzoic  acid. 

Rearrangement  of  2-Ethylmercapto-^-brom-6-thiocyanpyrimi- 
dine  into  the  Isothiocyanate: — About  0.2  gram  of  the  thiocyanate 
was  heated  for  2  hours  at  i5O°-i6o°.  We  obtained  a  red  oil 
which  solidified  on  cooling  and  melted  at  75°-8o°.  That  a 
rearrangement  had  taken  place  was  shown  in  the  following 
manner:  The  compound  (melting  at  75°-8o°)  reacted  at  once 
with  ammonia,  giving  2-ethylmercapto-5-brom-6-thiourea- 
pyrimidine2  melting  at  2i9°-22O°.  A  mixture  of  the  two 
preparations  melted  at  the  same  temperature. 

NH— CO 

I  I 
2-Orthotoluidino-6-oxypyrimidine,   o-CH3.C6H4NH.C       CH. — 

II  II 
N — CH 

Bighteen  grams  of  2-ethylmercapto-6-oxypyrimidine  and  one 
molecular  proportion  of  orthotoluidine  (14  grams)  were  heated 
together  on  the  steam  bath  for  3  days.  The  evolution  of 

1  Wheeler  and  Bristol:  Loc.  cit. 
*  Ibid. 


Researches  on  Pyrimidines.  141 

mercaptan  was  then  complete  and  a  compound  was  obtained 
which  was  difficultly  soluble  in  alcohol.  It  crystallized  from 
hot  alcohol  or  acetic  acid  in  prismatic  crystals  melting  at 
2i9°-22o°.  It  was  soluble  in  alkali.  Analysis  (Kjeldahl)  : 

Found. 
Calculated  for  CUHUON3.  I.  II. 

N  20.89  20.93  20-74 


2-Orthotoluidino-6-chlorpyrimidine,     o-CH3.C6H4NH.C       CH. 

II        II 
N  —  CH 

—  Ten  grams  of  2-orthotoluidino-6-oxypyrimidine  were  heated 
on  the  steam  bath  with  25  cc.  of  phosphorus  oxychloride  until 
the  evolution  of  hydrochloric  acid  gas  ceased.  The  excess  of 
phosphorus  oxychloride  was  then  distilled  under  diminished 
pressure.  We  obtained  a  yellow  oil,  which  assumed  a  crystal- 
line form  when  treated  with  ammonia.  The  compound 
crystallized  from  alcohol  in  corpuscular  crystals  melting  at 
78  °.  It  was  insoluble  in  alkali.  Analysis  (Kjeldahl)  : 

Found. 
Calculated  for  CnH10N3Cl.  I.  II. 

N  19.1  18.8  18.92 

Action  of  Potassium  Thiocyanate  on  2-Orthotoluidino-6- 
chlorpyrimidine:  —  Four  grams  of  the  chlorpyrimidine  and  3 
grams  of  potassium  thiocyanate  were  dissolved  in  50  cc.  of 
alcohol  and  the  solution  boiled  for  2  hours.  After  filtering  a 
small  amount  of  insoluble  material  the  excess  of  alcohol  was 
evaporated  on  the  steam  bath.  We  obtained  a  crystalline 
residue  which  crystallized  from  alcohol  and  melted  at  77°-78°. 
It  responded  to  a  test  for  chlorine  and  was  identified  as  the 
unaltered  chloride.  Analysis  (Kjeldahl): 

Calculated  for  CuH10N3Cl.  Found. 

N  19.1  19.07 

2-Orthotoluidino-6-aminopyrimidinet 
N^CNH, 

I  I 

0-CH3.C6H4NHC       CH.  —  2-Orthotoluidino-6-chlorpyrimidine 

II  II 
N  —  CH 


142  Johnson  and  Storey. 

does  not  react  with  ammonia  at  ordinary  temperature. 
When  heated  with  alcoholic  ammonia  for  2  hours  at  140°- 150° 
it  gave  a  quantitative  yield  of  the  aminopyrimidine.  This 
was  very  soluble  in  alcohol  and  crystallized  from  dilute  alcohol 
in  aggregates  of  small  prisms  melting  at  124°.  Analysis 
(Kjeldahl) : 

Calculated  for  CnHi2N4.  Found. 

N  28.00  27.7 

2-Orthotoluidino-6-anilinopyrimidine, 
N  =  CNHC6H5 

o-CH3C6H4NHC       CH.— Three       grams       of        2-orthotolui- 

II        II 
N  — CH 

dino-6-chlorpyrimidine  and  4  grams  of  aniline  were  dissolved 
in  25  cc.  of  benzene  and  the  solution  boiled  for  6  hours.  It 
was  then  filtered  and  evaporated  to  dryness.  We  obtained  a 
crystalline  residue  which  was  washed  with  water  to  remove 
aniline  hydrochloride  and  then  dissolved  in  warm  dilute  hydro- 
chloric acid.  The  hydrochloride  of  the  anilinopyrimidine 
crystallized,  on  cooling,  in  slender  needles  melting  at  126°. 
Analysis  (Kjeldahl): 

Calculated  for  C17H16N4.HC1.  Found. 

N  17.92  17.73 

When  the  hydrochloride  was  dissolved  in  water  and  ammonia 
added  to  the  solution  the  free  base  separated.  It  crystallized 
from  dilute  alcohol  in  hexagonal  plates  melting  at  128°  to  a 
clear  oil.  Analysis  (Kjeldahl) : 

Calculated  for  C^H^N^  Found. 

N  20.28  20.29 

NH  — CO 

I  I 

s-Paratoluidino-d-oxypyrimidine,  />-CH3.C6H4NHC          CH. — 

I!         il 

N CH 

This  compound  is  formed,  in  a  smooth  manner,  by  heating 
2-ethylmercapto-6-oxyprimidine  with  a  molecular  proportion 
of  paratoluidine  at  100°.  It  was  difficultly  soluble  in  warm 
alcohol,  acetone,  boiling  water,  and  cold  acetic  acid.  It  crystal- 


Researches  on  Pyrimidines.  143 

lized  from  acetic  acid  in  clusters  of  needles  melting  at  270°- 
271°.     Analysis  (Kjeldahl)  : 

Calculated  for  CiiHuON3.  Found. 

N  20.89  21.0 


2-Paratoluidino-6-chlorpyrimidine,  />-CH3C6H4NH.C       CH.— 

II       I! 

N  —  CH 

Twenty-six  grams  of  2-paratoluidino-6-oxypyrimidine  were 
digested  with  65  cc.  of  phosphorus  oxychloride  until  the  evolu- 
tion of  hydrochloric  acid  gas  ceased.  We  obtained  a  dark 
colored  solution  which  was  heated  at  100°  under  diminished 
pressure  to  remove  the  excess  of  phosphorus  oxychloride. 
The  residue  was  dissolved  in  ice  water  and  the  solution  made 
alkaline  with  ammonia  when  the  chlorpyrimidine  deposited. 
It  crystallized  from  alcohol  in  prisms  melting  at  112°-  113°  to 
an  oil.  Analysis  (Kjeldahl)  : 

Calculated  for  CiiH10N3Cl.  Found. 

N  19.13  18.99 

Action  of  Potassium  Thiocyanate  on  2-Paratoluidino-6- 
chlor  pyrimidine:  —  This  pyrimidine  was  recovered  unaltered, 
melting  at  ii2°-ii3°,  after  warming,  in  acetone  solution,  with 
potassium  thiocyanate  for  2.5  hours. 

2-Paratoluidino-6-anilinopyrimidine, 
N  =  CNHC6H5 

£-CH3C6H4NHC       CH.—  The    hydrochloride     of     this     base 

II        II 
N  —  CH 

was  obtained  when  2-paratoluidino-6-chlorpyrimidine  was 
warmed  in  benzene  with  aniline.  The  salt  was  very  soluble 
in  hot  water  and  alcohol.  It  crystallized  from  alcohol  in  prisms 
which  decomposed  at  134°.  Analysis  (Kjeldahl)  : 

Calculated  for  Ci7Hi6N4.HCl.  Found. 

N  17.92  17.96 

When  sodium  hydroxide  was  added  to  an  aqueous  solution 
of  this  salt  the  pyrimidine  base  deposited  in  needles.  It  was 


144  Johnson  and  Storey. 

insoluble  in  hot  water,  and  crystallized  from  alcohol  in  needles 
melting  at  135°  to  an  oil.  Analysis  (Kjeldahl) : 

Calculated  for  Ci7H16N4.  Found. 

N  20.28  20.15 

NH  — CO 

I  I 
2-£}-Naphthylamino-6-oxypyrimidine,  /?-C10H7NH.C         CH. — 

II  II 
N CH 

From  /?-naphtylamine  and  2-ethylmercapto-6-oxypyrimidine. 
It  was  insoluble  in  hot  water  and  difficultly  soluble  in  alcohol. 
It  crystallized  from  alcohol  in  clusters  of  needles  melting 
at  270°.  Analysis  (Kjeldahl) : 

Calculated  for  Ci4HuON3.  Found. 

N  17.72  17.77 

2-Paratolyi-4-methyl-6-chlorpyrimidine, 
N  ==CC1 

I  I 

£-CH3C6H4.C       CH.— This  chloride  was  prepared  by  heating 

II  II 

N  —  CCH3 

on  the  steam  bath  15  grams  of  2-paratolyl-4-methyl-6-oxy- 
pyrimidine1  with  17  grams  of  phosphorus  pentachloride  and 
about  20  cc.  of  phosphorus  oxychloride  for  7  hours.  A  dark 
colored  solution  was  obtained  which  was  slowly  poured  upon 
crushed  ice  to  destroy  the  phosphorus  halides.  The  chlorpy- 
rimidine  separated  at  once,  and  crystallized  from  alcohol  in 
beautiful  prisms  melting  at  107°  to  a  clear  oil.  Analysis 
(Kjeldahl) : 

Found. 
Calculated  for  CuHuNgCl.  I.  II. 

N  12. 81  12.75  12.83 

2-  Paratolyl-4-methyl-6-thiocyanp  yrimidine , 
N  =  C.SCN 

I  I 

/>-CH3C6H4C       CH.— An    alcoholic    solution    (30    cc.)    of    4 

II  II 

N  —  CCH3 
grams  of    2-paratolyl-4-methyl-6-chlorpyrimidine  and  3  grams 

1  Loc.  cU. 


Researches  on  Pyrimidines.  145 

of  potassium  thiocyanate  was  boiled  for  1.5  hours.  The  in- 
soluble potassium  chloride  was  removed  by  filtration,  and  the 
solution  cooled,  when  the  thiocyanate  separated  in  irregular 
prisms.  It  crystallized  from  alcohol  in  fern- shaped  crystals 
melting  at  123°.  When  warmed  with  aniline  or  aqueous 
ammonia  at  100°  it  was  recovered  unaltered.  Analysis 
(Kjeldahl) : 

Calculated  for  Ci8HnN3S.  Found. 

N  17.42  17-2 

2-Paratolyl~4-methyl-  6-thiopyrimidine , 
NH  — CS 

I  I 

/>-CH3C6H4C          CH. — This    compound    was    obtained    when 

II  II 

N CCH3 

2-paratolyl-4-methyl-6-thiocyanpyrimidine  was  gently  warmed 
with  one  molecular  proportion  of  thiobenzoic  acid.  It  depos- 
ited from  alcohol  in  slender  prisms  melting  at  114°.  Analysis 
(Kjeldahl) : 

Calculated  for  Ci2Hi2N2S.  Found. 

N  12.96  12. 81 

Rearrangement  of  2-Paratolyl-4-methyl-6-thiocyanpyrimidine 
into  the  Isothiocyanate: — One  and  five- tenths  grams  of  the 
thiocyanate  were  heated,  in  an  oil  bath,  for  2.5  hours  at  130°- 
I35°-  We  obtained  a  thick  oil  which  slowly  crystallized  after 
cooling.  The  compound  was  very  soluble  in  warm  alcohol 
and  on  cooling  crystallized  in  radiating  prisms  melting  at 
2O7°-2o8°.  It  did  not  react  with  ammonia  and  a  nitrogen 
determination  agreed  with  the  calculated  value  for  the  iso- 
thiocyanate.  It  probably  is  a  polymeric  form  of  the  iso- 
thiocyanate,  (C^nNgS),.  Analysis  (Kjeldahl) : 

Calculated  for  (CisHnNsS)*.  Found. 

N  17.42  17-35 

In  a  second  experiment  the  thiocyanate  was  heated  for  2 
hours  at  130°- 135°,  cooled,  and  then  suspended  in  aqueous 
ammonia  for  2  days.  We  obtained  a  yellow  amorphous  pro- 


146  Johnson  and  Storey. 

duct  which  crystallized  from  alcohol  in  irregular  prisms  melting 
at  1  45°-  1  46°.  A  nitrogen  determination  agreed  with  the 
calculated  value  for 

2-Paratolyl-4-methyl-6-thioureapyrimidine, 


/>-CH3C6H4C       CH.— 

II       II 
N  —  CCH8 

Calculated  for  C^H^^S.  Found. 

N  21.70  21.45 

2-Paratolyl-4-methyl-6-aminopyrimidine, 

N=C.NH, 

I  I 

/>-CH3C6H4C       C.H.  —  2-Paratolyl-4-methyl-6-chlorpyrimidine 

II  II 

N  —  C.CH3 

was  recovered  unaltered  after  heating  with  alcoholic 
ammonia  for  2  hours  at  120°  and  again  for  2  hours  at  i5O°-i6o°. 
When  heated  with  ammonia  at  i8o°-i9o°  for  2  hours  a  good 
yield  of  the  aminopyrimidine  was  obtained.  It  deposited 
from  alcohol  in  hexagonal  tables  melting  at  I78°-I79°.  An- 
alysis (Kjeldahl)  : 

Calculated  for  C12H18N3.  Found. 

N  21.10  2  I.  O6 

2-Paratolyl-4-methyl-6-anilinopyrim<idine, 
N  =  CNHC6H5 

£-CH3C6H4C       CH.—  The       hydrochloride      of      this      base 

II        II 

N  —  CCH, 

was  obtained  when  i  gram  of  2-paratolyl-4-methyl-6-chlor- 
pyrimidine  and  i  gram  of  aniline  were  warmed  in  benzene  for 
6  hours.  The  salt  crystallized  from  alcohol  in  clusters  of 
needles  melting  at  269°-27o°  with  effervescence.  Analysis 
(Kjeldahl)  : 

Calculated  for  C18Hi7N3.HCl.  Found. 

N  13.48  13-44 


Researches  on  Pyrimidines. 


147 


The  base  crystallized  from  alcohol  in  needles  melting  at 
I20°-i2i°  to  an  oil.     Analysis  (Kjeldahl) : 

Calculated  for  Ci8H17N3.  Found. 

N  15.27  15.17 

NEW  HAVEN,  CONN., 
March  1,  1908. 


[Reprinted  from  the  American  Chemical  Journal,  Vol.  XL,. 
No.  3.    September,  1908.] 


[Contributions  from  the  Sheffield  Laboratory  of  Yale  University.] 

CLVIII.  —  RESEARCHES   ON   PYRIMIDINES:      SYN- 
THESIS OF  CYTOSINE-5-CARBOXAMIDE. 

[THIRTY-SIXTH  PAPER.1] 
BY  HENRY  I,.  WHEELER  AND  CARL  O.  JOHNS. 

In  our  previous  papers  on  the  synthesis  of  the  5-carboxyl 
rivatives  of  uracil2  and  cytosine3  we  have  shown  that  Clais- 
t's  ethoxymethylenemalonic  ester,4  C2H5OCH  =  C(CO2C2H5)2> 

1  A  complete  list  of  our  previous  papers  on  pyrimidines  up  to  the  end  of  the  year 
1907  is  given  at  the  end  of  this  article. 

2  THIS  JOURNAL,  37,  392  (1907). 
»  Ibid.,  38,  594  (1907). 

*  Ann.  Chem.  (Liebig),  297,  75  (1897). 


234  Wheeler  and  Johns. 

condenses  in  alkaline  solution  with  2-ethylpseudothiourea, 
H2N — C(SC2H5)  =  NH,  giving  2-ethylmercapto-5-carbethoxy-6- 
oxypyrimidine  (Formula  I.,  on  page  237).  The  condensation 
is  especially  smooth.  We  have  succeeded  in  greatly  increasing 
the  yield  of  pyrimidine  over  the  amount  obtained  in  our  first 
experiments  and  this  condensation  now  offers  an  excellent 
starting  point  for  further  syntheses.  We  have  also  pre- 
viously shown  that  2-ethylmercapto-5-carbethoxy-6-oxypyrimi- 
dine  is  easily  saponified  by  alkali  and  the  yield  of  2-ethyl- 
mercapto-6-oxypyrimidine-5-carboxylic  acid,  II.,  is  very  good. 

We  now  find  that  with  proper  precautions  this  mercapto 
acid  can  be  practically  quantitatively  converted  into  the  acid 
chloride  of  2-ethylmercapto-6-chlorpyrimidine-5-carboxylic 
acid,  III.  This  acid  chloride  is  a  very  reactive  substance  and, 
as  might  be  expected,  the  chlorine  attached  to  the  CO  group 
is  more  reactive  than  that  in  the  6  position. 

When  the  dichloride  is  treated  with  cold  aqueous  ammonia 
one  chlorine  atom  is  replaced  by  the  amino  group  and  2-ethyl- 
mercapto-6-chlorpyrimidine-5-carboxamide,  IV.,  results.  This 
is  proved  by  the  fact  that  on  treating  the  chloramide  with 
sodium  ethylate  an  ethoxy  derivative,  V.,  is  obtained  which 
is  isomeric  and  not  identical  with  2-ethylmercapto-5-carbeth- 
oxy-6-aminopyrimidine,  X. 

When  the  dichlorpyrimidine  is  warmed  with  concentrated 
aqueous  ammonia  on  the  steam  bath,  both  chlorine  atoms 
are  removed  and  it  is  quantitatively  converted  into  2-ethyl- 
mercapto-6-aminopyrimidine-5-carboxamide,  VI. 

We  have  found  that  this  acid  amide  combines  with  bro- 
mine with  the  evolution  of  heat  and  that  the  product  has  the 
properties  and  composition  of  a  dibrom  addition  product, 
VII.  When  it  was  treated  with  alkali  it  regenerated  unal- 
tered 2-ethylmercapto-6-aminopyrimidine-5-carboxamide. 

When  it  was  heated  under  certain  conditions,  its  loss  in 
weight  and  percentage  of  nitrogen  corresponded  with  that  re- 
quired for  the  formation  of  a  monobromamide.  If  a  mono- 
bromamide  was  formed  here  it  might  be  expected  that,  in 
common  with  such  substances,  on  treatment  with  alkali  the 
bromamide  group,  RCONHBr,  would  undergo  a  rearrange- 


Researches  on  Pyrimidines.  235 

ment  into  the  carbonamide  form,  RNCO.  In  this  case  the 
reactive  grouping  would  probably  unite  with  the  adjacent 
amino  group  in  the  6  position,  forming  a  five  membered 
ring,  with  the  result  that  an  8-oxypurine  would  be  obtained. 

When  the  product  or  mixture  obtained  by  heating  the  di- 
brom  addition  product  was  treated  with  aqueous  alkali,  cyto- 
sine-5-carboxylic  acid,  VIII.,  sometimes  2-ethylmercapto-6- 
aminopyrimidine-5-carboxamide,  VI.,  and  a  product  free 
from  sulphur  was  obtained.  This  latter  substance  and  its 
salts  gave  results  on  analysis  which  closely  agreed  with  the 
calculated  for  2,8-dioxypurine,  XI.,  the  only  one  of  the  di- 
oxypurines  that  has  not  been  described.  The  empirical  formula  of 
2,8-dioxypurine,  C5H4O2N4,  differs  fromcytosine-5-carboxamide, 
IX.,  C5H6O2N4,  by  only  two  hydrogen  atoms.  The  percentage 
composition  of  these  substances  is  therefore  so  closely  similar 
that  the  analysis  did  not  decide  which  one  of  the  two  we  were 
dealing  with.  In  our  previous  work  we  had  reason  to  be- 
lieve that  we  had  obtained  cytosine-5-carboxamide,  IX. 
With  the  object  of  preparing  this  substance,  the  behavior  of 
the  ethyl  ester  of  cytosine-5-carboxylic  acid,  or  5-carbethoxy- 
cytosine,  XII.,  with  aqueous  ammonia  was  examined  at  that 
time  and  it  was  found  that  this  ether  showed  an  exceptional 
inertness.  On  heating  at  140°  to  150°  for  two  hours,  about 
25  per  cent  remained  unaltered.  On  concentrating  the  mother 
liquor  more  soluble  material  crystallizing  in  needles  was  ob- 
tained. The  analytical  results  in  this  case  and  the  method 
of  preparation  were  then  taken  to  indicate  that  the  expected 
cytosine-5-carboxamide  had  been  obtained.  Owing  to  the 
poor  yield,  nothing  further  was  done  with  this  substance. 

This  material  was  not  identical  with  that  obtained  in  the 
present  work.  The  facts  then  seemed  to  show  that  the  ma- 
terial obtained  from  the  brom  addition  product,  VII.,  was 
2,8-dioxypurine.  The.  question  was  finally  settled  in  the  nega- 
tive, as  follows:  The  material  obtained  by  heating  the  di- 
bromamide  and  then  treating  with  alkali  was  carefully  freed 
from  2-ethylmercapto-6-aminopyrimidine-5-carboxamide  and 
cytosine-5-carboxylic  acid.  It  was  then  boiled  with  strong 
hydrochloric  acid  and  found  to  completely  decompose  into 
cytosine-5-carboxylic  acid. 


236  Wheeler  and  Johns. 

This  shows  that  no  Hofmann  rearrangement  had  taken  place 
and  that  the  present  substance  is  the  true  cytosine-5-carbox- 
amide. 

The  inertness  of  5-carbethoxycytosine,  and  also  of  2,6- 
diamino-5-carbethoxypyrimidine,1  on  heating  with  ammonia, 
is  comparable  with  that  of  the  dialkylmalonic  esters.2  The 
ammonium  salts  of  these  acids  break  down  with  the  evolu- 
tion of  carbon  dioxide,  and  since  5-carbethoxycytosine  is  a 
substituted  malonic  acid  derivative  this  offers  an  explana- 
tion of  our  previous  results.  The  material  formerly  viewed 
as  cytosine-5-carboxamide  was  probably  impure  or  partly 
hydrous  cytosine. 

It  is  probable  that  no  monobromamide  was  formed  on  heat- 
ing the  dibrom  addition  product  and  that  the  dibrom  addi- 
tion product  has  the  bromine  atoms  attached  to  the  double 
bond  between  the  4  and  5  positions.  Similar  additions  of 
bromine  to  the  double  bond  have  been  observed  in  other 
cases  in  this  laboratory,  e.  g.,  thymine  and  4,5-dimethyluracil. 
The  compounds  in  general  have  little  stability.  An  unusually 
stable  dibrom  addition  product  of  this  sort,  prepared  from 
2-phenylhydrazine-4-methyl-6-oxypyrimidine,  has  been  de- 
scribed by  Pellizzari  and  Roncagliolo.8 

When  2-ethylmercapto-6-aminopy rimidine-5-c a r b  o x amide, 
VI.,  was  boiled  with  hydrochloric  acid  it  was  converted  into 
cytosine-5-carboxylic  acid.  When  given  a  less  energetic 
treatment  with  acid,  in  addition  to  unaltered  material,  some 
cytosine-5-carboxamide  along  with  cytosine-5-carboxylic  acid 
was  obtained.  This  amide  was  identical  with  that  obtained 
from  the  brom  product. 

The  question  whether  or  not  the  Hofmann  rearrangement 
can  be  applied  in  the  pyrimidine  series  still  remains  to  be 
investigated.  A  2-oxygen  amide  such  as  cytosine-5-carbox- 
amide,  being  soluble  in  alkali  and  free  from  sulphur,  would 
be  a  more  promising  substance  than  the  mercaptoamide  to 
decide  this  question.  The  work  will  be  undertaken  as  soon 

1  THIS  JOURNAL,  38,  598  (1907). 

2  Fischer  and  Dilthey:  Ber.  d.  chem.  Ges.,  35,  844. 
a  Gaz.  chim.  ital.,  31, 1,  513. 


Researches  on  Pyrimidines. 


237 


as  a  more  convenient  method  of  preparing  this  amide,   in 
quantities  sufficient  for  synthetical  purposes,  is  obtained. 

It  appears  from  the  above  results  that  the  unsaturated 
condition  of  the  molecule,  or  the  double  bond  in  the  4,5  posi- 
tion, interferes  with  the  Hofmann  rearrangement,  at  least 
in  the  case  of  2-ethylmercapto-6-aminopyrimidine-5-carbox- 

amide. 


HN  — CO 
LSC 


CCOAH5 


N  — CH 

I. 

N  =  C  —  NH2 


HN  — CO 
CjHgSC       CCOOH 


N==cq 

C2H6SC      CCOC1 


N  — CH 
II. 


N  — CH 
III. 


0.1 *•"  **1  I  I 

2H5SC       icONH2    <-    C2H5SC       CCONH2 


CCONH2 


N  — CH 

VI. 


N  — CH 

IV. 


*f 

— 

N        .      Br 
N  — CHBr 


=  C  —  NH2 
|    /CONH2 


N  =  C  — NH, 
OC       CCONH2 


HN  — CH 

IX. 


N  =  C  —  NH2 

OC       CCOOH 

1        II 
HN  —  CH 


VIII. 


1        1  / 

oc       c-  NH/ 


HN  —  CH 

XI. 


C0 


N  — CH 
v. 


N  =  C  — NH2 

C2H6SC      CCOOC.H. 

II        II 
N  — CH 
X. 

N=-C  — NH, 

OC      CCOOCjH, 

I        II 
HN— CH 

XII. 


EXPERIMENTAL  PART. 

Ethoxymethylenemalonic  Ester,  C2H6OCH  =  C(CO2C2H5)2.  — 
Since  this  ester  has  proved  to  be  of  special  importance  for 
pyrimidine  syntheses  a  detailed  account  is  given  of  our 
methods  of  preparing  and  employing  the  substance. 


238  Wheeler  and  Johns. 

The  ester  was  prepared  essentially  according  to  Claisen's 
directions.1  We  have  found  that  the  mixture  of  malonic 
ester  (100  grams),  orthoformic  ester  (93  grams),  acetic  anhy- 
dride (128  grams),  and  zinc  chloride  (7  grams)  reacts  imme- 
diately on  gently  warming  and  enough  heat  is  evolved  to  boil 
the  solution.  The  mixture  was  kept  boiling  for  an  hour,  then 
all  that  distilled  up  to  110°  at  ordinary  pressure  (the  bulb 
of  the  thermometer  being  in  the  solution)  was  removed.  The 
distillate  usually  weighed  about  52  grams  and  represented 
the  ethyl  acetate  formed  in  the  reaction.  A  little  anhydride 
was  usually  carried  over. 

It  was  found  that  it  is  unnecessary  to  boil  the  above  mix- 
ture for  1 1- 1 2  hours,  as  stated  by  Claisen.  In  fact,  heating 
the  flask  attached  to  a  return  condenser  in  an  oil  bath  at  120°- 
130°,  or  so  that  the  mixture  boiled  gently,  for  two  more  hours 
was  sufficient.  There  were  then  obtained  14-15  grams  of 
impure  ethyl  acetate  or  about  67  grams  in  all,  which  is  60  per 
cent  of  the  calculated.  The  calculated  yield  of  ethyl  acetate 
is  no  grams.  Boiling  for  a  longer  time  gave  very  little  more 
ethyl  acetate.  A  portion  of  the  ethyl  acetate,  however,  proba- 
bly remains  behind  in  the  mixture. 

The  mixture  was  then  distilled  at  15-20  mm.  pressure  and 
in  almost  every  case  60-62  grams  of  ethoxymethylenemalonic 
ester  were  obtained.  Sixty-two  grams  of  ethoxymethylene- 
malonic ester  is  only  45.9  per  cent  of  the  calculated.  How- 
ever, this  yield  is  in  perfect  agreement  with  Claisen's  state- 
ment that  500  grams  of  malonic  ester,  in  five  portions,  gave 
307  grams  of  distilled  ethoxymethylenemalonic  ester.  The 
amount  of  ethyl  acetate  obtained  indicated  that  at  least  81 
grams  of  ethoxymethylenemalonic  ester  was  formed  from 
100  grams  of  malonic  ester. 

We  have  now  found  that  it  is  not  necessary  or  even  advisa- 
ble, on  account  of  loss,  to  prepare  pure  distilled  ethoxymethyl- 
enemalonic ester  for  the  present  condensation.  In  fact,  a 
much  better  yield  of  condensation  product  is  obtained  if  the 
oil  is  not  distilled. 

1  Ann.  Chem.  (Liebig),  297,  75  (1897). 


Researches  on  Pyrimidines.  239 

Preparation  of  the  Potassium  Salt  of  2-Ethylmercapto-^-carb- 

HN  — CO 

I  I 
ethoxy-6-oxypyrimidine,  C.jH5SC        CCO2CjH5. — In  one  experi- 

II  II 
N— CH 

ment,  after  heating  the  above  mixture  at  ordinary  pressure  for 
three  hours,  distilling  the  ethyl  acetate  as  stated,  and  filtering 
from  zinc  chloride,  everything  was  then  removed  that  dis- 
tilled below  117°  at  about  20  mm.  pressure.  The  residue 
in  this  case  weighed  105  grams.  This  was  added  to  100 
grams  of  the  addition  product  of  ethyl  bromide  and  thio- 
urea  dissolved  in  100  cc.  of  water.  To  this  cold  solution 
60  grams  of  potassium  hydroxide  in  120  cc.  of  water  were  slowly 
added  and  the  mixture  was  not  allowed  to  warm.  The  solution 
soon  became  semisolid  from  the  separation  of  the  potassium 
salt.  It  was  found  that  more  separated  on  standing.  The 
mixture  was  allowed  to  stand  for  two  days  at  ordinary  tem- 
perature. The  salt  which  separated  then,  on  filtering  and 
drying,  weighed  113  grams,  or  nearly  twice  as  much  crude 
salt  as  was  obtained  from  100  grams  malonic  ester  in  our 
previous  work. 

In  another  experiment  everything  was  removed  that  distilled 
below  120°  at  25  mm.  pressure.  The  remaining  oil  weighed 
100  grams.  When  this  was  condensed  with  2-ethylpseudo- 
thiourea  as  above,  the  weight  of  the  potassium  salt,  after 
washing  with  a  little  alcohol,  was  91  grams. 

The  above  yields,  of  course,  do  not  represent  the  weights  of 
pure  substances,  they  merely  serve  to  give  a  general  idea.  We 
conclude,  however,  that  the  above  process  yields  almost  75 
per  cent  of  the  calculated  of  ethoxymethylenemalonic  ester; 
105  grams  is  77.7  per  cent  of  the  calculated. 

Preparation  of  2-Ethylmercapto-6-oxypyrimidine-5-carboxylic 
HN  — CO 

Acid,  C2H5SC       CCOOH.— The    crude    potassium    salt    of 

II        II 
N  — CH 
2-ethylmercapto-5-carbethoxy-6-oxypyrimidine  was  saponified 


240  Wheeler  and  Johns. 

by  warming  with  potassium  hydroxide.  For  about  27-30 
grams  of  this  salt  15  grams  of  potassium  hydroxide  were  used. 
If  a  smaller  proportion  of  alkali  was  used  the  saponification 
was  liable  to  be  less  smooth. 

The  potassium  salt  was  dissolved  in  alcohol,  the  alkali  in 
water  added,  and  the  solution  evaporated  to  dryness  on  the 
steam  bath.  The  residue  was  taken  up  in  water  and  evaporated 
again,  when  the  saponification  was  usually  found  to  be  com- 
plete. The  acid  was  then  precipitated  from  the  filtered  aque- 
ous solution  of  this  residue  by  means  of  hydrochloric  acid. 
It  separated  in  an  almost  pure  condition  as  shown  by  its  melting 
point  (near  167°).  Care  must  be  taken  not  to  add  too  much 
hydrochloric  acid  since  the  mercapto  acid  is  soluble  in  a  certain 
excess.  On  the  other  hand,  if  the  solution  is  not  made  dis- 
tinctly acid,  the  potassium  salt  of  2-ethylmercapto-6-oxy- 
pyrimidine-5-carboxylic  acid  is  obtained.  This  melts  with 
effervescence  above  250°.  If  the  precipitate  melts  near  131° 
the  saponification  is  not  complete. 

Twenty-seven  grams  of  the  washed  potassium  salt  gave 
17  grams  of  2-ethylmercapto-6-oxypyrimidine-5-carboxylic 
acid.  The  same  quantity  of  salt  in  another  experiment  gave 
1  8  grams  of  acid.  This  is  88.6  per  cent  of  the  calculated. 

The   Acid   Chloride   of   2-Ethylmercapto-6-chlorpyrimidine-5- 


carboxylic  Acid,   C^HgSC        CCOC1.—  The    best    yield  of  this 

I!       II 

N  —  CH 

compound  was  obtained  when  perfectly  dry  2-ethylmercapto- 
oxypyrimidine-5-carboxylic  acid  and  phosphorus  oxychloride 
were  mixed  in  the  proportion  of  5  cc.  of  the  chloride  to  i  gram 
of  the  acid  and  then  heated,  with  a  return  condenser,  in  an  oil 
bath.  The  temperature  of  the  bath  was  kept  at  i3o°-i5O°  or 
so  that  the  solution  boiled  quietly  and  until  hydrogen  chloride 
was  no  longer  evolved.  This  required  from  2  to  3  hours, 
although  solution  took  place  soon  after  heating.  Most  of  the 
phosphorus  oxychloride  was  then  removed  under  reduced 
pressure  at  100°  and  the  residue,  a  thick  oil,  was  poured  upon 


Researches  on  Pyrimidines.  241 

cracked  ice.  It  then  changed  to  a  granular  solid.  The  yield 
of  crude  chloride  was  85  per  cent  of  the  calculated.  To  prepare 
the  amide  of  2-ethylmercapto-6-aminopyrimidine-5-carboxylic 
acid,  instead  of  pouring  on  ice,  it  is  poured  directly  into  con- 
centrated ammonia  (see  below).  The  yield  of  crude  amide 
is  then  almost  quantitative.  In  another  experiment  18  grams 
of  the  acid  and  45  cc.  of  phosphorus  oxychloride  were  boiled 
on  a  sand  bath.  Under  these  conditions  the  material  was 
completely  decomposed.  The  yield  of  this  chloride  may  vary 
decidedly  under  slight  changes  of  conditions. 

This  acid  chloride  was  very  soluble  in  cold  benzene,  ether, 
and  ligroin.  It  was  purified  for  analysis  by  dissolving  in  ligroin 
and  evaporating  at  the  temperature  of  the  room.  Radiating 
clusters  of  colorless  prisms  were  formed,  which  melted  to  a 
clear  oil  at  38°-4O°.  Analysis: 

Calculated  for 
C7H6ON2C12S.  Found. 

N  11.81  11.76 

The  Amide  of  2-Ethylmercapto-6-chlorpyrimidine-5-carboxylic 


I 
SC 


Acid,  C2H5SC       CCONH,.—  This  is  the  first  product  obtained 

II         II 

N  —  CH 

by  the  action  of  aqueous  ammonia  on  the  above  acid  chloride. 
When  the  acid  chloride  was  added  to  cold  concentrated  aqueous 
ammonia,  an  immediate  reaction  took  place  with  the  liberation 
of  heat  and  a  white  powder  was  formed.  This  was  washed 
with  water  to  remove  ammonium  chloride.  When  dried  it 
was  found  to  be  moderately  soluble  in  hot  alcohol,  benzene,  and 
toluene,  and  difficultly  soluble  in  boiling  ether.  It  crystallized 
from  benzene  in  long,  hairlike  crystals  which  formed  a  fibrous 
mat.  It  then  melted  sharply  to  a  colorless  oil  at  134°  and  the 
yield  was  almost  quantitative.  Analysis: 

Calculated  for  Found. 

C7H8ON8C1S.  I.  II. 

N  19.31  19.36  19-24 

When  this  chloramido  compound  was  first  obtained  it  became 
a  question  which  chlorine  atom  had  been  replaced  in  the  above 


242  Wheeler  and  Johns. 

acid  chloride.  In  order  to  decide  this  point,  two  grams  of  the 
chloramido  compound  were  dissolved  in  absolute  alcohol  and 
added  to  a  solution  of  0.25  gram  of  sodium,  also  in  alcohol. 
An  immediate  precipitate  resulted  and  heat  was  liberated. 
On  cooling,  a  mass  of  well  defined  prisms  separated.  The 
sodium  chloride  was  removed  by  washing  with  water.  The 
residue  was  then  found  to  be  insoluble  in  hot  water  but  it 
crystallized  from  alcohol,  in  which  it  was  moderately  soluble. 
The  substance  melted  at  134°,  the  same  temperature  as  the 
chloramido  compound.  However,  it  was  free  from  chlorine 
and  when  mixed  with  the  chloramido  compound  the  melting 
point  of  the  mixture  was  lowered  about  30°.  The  yield  and 
nitrogen  determinations  agreed  with  the  calculated  for  an 
ethoxy  derivative. 

Calculated  for  Found. 

C9Hi302N8S.  I.  II. 

N  18.50  18.54  18.45 

This  ethoxy  derivative  should  have  the  structure  represented 
by  one  of  the  following  formulas: 

N  =  C  —  NH2  N  — COC2H5 

C       CCO.OC2H5  C2H5SC       CCO.NH2. 

II        II  II        II 

N  — CH  N  — CH 

I.  II. 

The  first  of  these  two  compounds  has  already  been  described 
by  us  in  our  twenty-sixth  paper,  p.  597.  It  melts  at  102  °.  To 
the  ethoxy  compound  now  obtained,  melting  at  134°,  is  there- 
fore assigned  the  structure  represented  by  formula  II.  It 
follows  that  the  chloride  from  which  it  was  prepared  has  the 
chlorine  atom  in  the  6  position  and  is  the  amide  of  2-ethyl- 
mercapto-6-chlorpyrimidine-5-carboxylic  acid. 

The  Amide  of  2-Ethylmercapto-6-aminopyrimidine-5-carboxylic 
N  =  C— NH2 

Acid,  CaH6SC       CCONH2.— If  the  acid    chloride  of  2-ethyl- 

II         II 
N  — CH 

mercapto-6-chlorpyrimidine-5-carboxylic  acid  is  warmed  with 


Researches  on  Pyrimidines.  243 

concentrated  ammonia  both  chlorine  atoms  are  replaced  by 
the  amino  group  and  the  amide  of  2-ethylmercapto-6-amino- 
pyrimidine-5-carboxylic  acid  is  formed.  We  have  prepared 
this  compound  by  slowly  adding  the  acid  chloride  (it  reacts 
vigorously)  to  a  considerable  excess  of  aqueous  ammonia  in 
an  evaporating  dish  and  then  warming  on  the  steam  bath. 
Not  very  much  of  the  aminoamide  thus  formed  dissolves  in 
the  hot  ammonia  nor  is  it  soluble  to  any  great  extent  in  boiling 
water.  It  should  be  warmed  until  the  insoluble  material 
melts  above  200°.  When  purified  by  crystallizing  from 
alcohol,  in  which  it  is  moderately  soluble,  it  separates  in  rec- 
tangular crystals,  little  stout  prisms  which  separate  slowly  and 
melt  to  an  oil  at  2i8°-2i9°.  It  is  soluble  in  glacial  acetic  acid 
but  insoluble  in  alkali.  The  yield  of  crude  product  melting 
at  214°  is  almost  quantitative.  Thirteen  grams  of  mercapto 
acid  gave  12  grams  of  this  amide.  Analysis: 

Calculated  for  Found. 

C7H10ON4S.  I.  II. 

N  .     28.28  27.99  27-9i 

Action  of  Hydrochloric  Acid. — When  this  amide  is  digested 
on  the  steam  bath  with  concentrated  hydrochloric  acid  ethyl 
mercaptan  is  evolved  and  the  amido  group  attached  to  the 
carboxyl  radical  in  position  5  is  removed.  If  the  resulting 
solution  is  allowed  to  cool  slowly  the  hydrochloride  of  cytosine- 
5-carboxylic  acid  separates  in  the  form  of  large  prisms  which 
contain  one  molecule  of  water  and  melt  sharply  at  276°  to  a 
brown  oil  and  with  some  effervescence.  This  salt  was  iden- 
tified by  its  properties  previously  described  and  by  the  fol- 
lowing analyses: 

Calculated  for 
C5H6O3N8.HC1.H2O.  Found. 

H20  8.59  8.75 

The  water  determination  was  made  by  heating  the  substance 
at  I20°-i3o°.  A  nitrogen  determination  then  gave  the  follow- 
ing results: 

Calculated  for 

C5H6O8N3.HC1.  Found. 

N  21.92  22.21 


244  Wheeler  and  Johns. 

Prolonged  digestion  of  the  aminoamide  with  dilute  hydro- 
chloric acid  or  potassium  hydroxide  also  removed  the  amido 
group  from  the  5  position.  For  a  description  of  the  less 
energetic  action  of  hydrochloric  acid  on  this  amide  see  under 
cytosine-5-carboxamide.  It  did  not  dissolve  in  a  solution  of 
potassium  hypobromite  (16  grams  of  bromine  in  280  cc.  of 
10  per  cent  alkali). 

The  Action  of  Dry  Bromine:  The  Dibrom  Addition  Product 
of  2-Ethylmercapto-6-amino-5-carboxamide, 
N  =  C  —  NH, 

I  I 

C2H5SC       CCONH2Br2.— This  compound  is  formed  by  adding 

II  II 
N  — CH 

the  amide  directly  to  liquid  bromine.  They  unite  with  evolu- 
tion of  considerable  heat.  Bight  grams  of  finely  powdered 
and  carefully  dried  amide  were  added  in  small  portions,  best 
through  a  sieve  to  prevent  the  formation  of  lumps,  to  about  15 
cc.  of  dry  bromine.  The  amide  then  dissolved  at  once  in  the 
bromine.  When  all  of  the  amide  had  been  added  the  excess  of 
bromine  was  allowed  to  evaporate  at  the  temperature  of  the 
room.  This  treatment  left  a  yellow,  crystalline  crust  that 
was  powdered  in  a  mortar  in  order  to  liberate  the  inclosed 
bromine.  The  yield  at  this  point  was  quantitative  if  care  was 
taken  to  exclude  moisture ;  otherwise  some  decomposition  took 
place.  Analyses  of  the  air-dried  material  gave  the  following 
results: 

Calculated  for  Found. 

C7H10ON4Br,S.  I.  II. 

N  15.64  15.50  15.91 

When  the  dibrom  addition  product  was  warmed  with  water 
unaltered  amide  was  obtained. 

Action  of  Alkali. — The  unaltered  amide  was  also  obtained  when 
this  material  was  treated  with  alkali.  One  gram  of  the  addi- 
tion product  was  added  to  10  cc.  of  water  containing  i  gram 
of  potassium  hydroxide.  Only  a  small  portion  dissolved  even 
after  heating  on  the  steam  bath.  On  filtering  and  acidifying 
the  filtrate  with  acetic  acid  a  very  small  amount  of  material 
not  soluble  in  ammonia  was  precipitated.  This  had  all  the 


Researches  on  Pyrimidines.  245 

properties  of  cytosine-5-carboxamide.  Its  hydrochloric  acid 
solution  gave  a  precipitate  with  nitric  acid. 

Behavior  on  Heating. — When  the  dibrom  addition  product 
was  heated  at  120°- 135°  a  point  was  finally  reached  where 
the  evolution  of  hydrogen  bromide  seemed  to  stop  or  proceed 
more  slowly.  The  brownish  white  material  then  agreed  in 
weight  with  the  loss  of  about  one  molecular  proportion  of 
hydrogen  bromide.  There  was  a  loss  from  13.5  grams  of  the 
addition  product  of  3.3  grams  while  the  calculated  loss  is  3.1 
grams.  Nitrogen  determinations  gave  the  following  results: 

Calculated  for  Found. 

C7H9ON4BrS.  I.  II. 

N  20. 2 i  20.47  20.76 

This  product  had  an  odor  similar  to  that  of  the  sulphur 
chlorides.  It  dissolved  only  partially  in  hot  water,  alcohol, 
ethyl  acetate,  or  amyl  acetate,  and  it  behaved  like  a  mixture  of 
more  or  less  decomposed  material.  It  dissolved  partially  in  a 
solution  of  sulphur  dioxide,  and  ammonia  then  precipitated 
unaltered  mercaptoaminoamide.  This  might  result  from  the 
hydrobromic  acid  salt  of  the  amide  possibly  contained  in  the 
mixture,  or  from  unaltered  dibrom  addition  product.  A 
solvent  suitable  to  isolate  a  monobromamide,  if  formed  here,  was 
not  found,  and  the  results  obtained  on  treating  the  material 
with  alkali  would  suggest  that  in  spite  of  the  analyses  such  a 
compound  was  not  formed.  Sometimes  the  product  would 
dissolve  completely  in  alkali.  When  dark  in  color  it  usually 
left  undissolved  amorphous,  dark  colored  decomposition  prod- 
ucts mixed  at  times  with  unaltered  mercaptoaminoamide. 

N  =  C— NH, 

Cytosine-5-carboxamide,  OC       CCONH2. — Ten    grams    of 

I         II 
HN  — CH 

the  brom  product  obtained  by  heating  the  above  dibrom 
addition  product  of  the  amide  of  2-ethylmercapto-6-amino- 
pyrimidine-5-carboxylic  acid  were  dissolved  in  50  cc.  of  water 
containing  10  grams  of  potassium  hydroxide.  In  this  particular 
experiment  complete  solution  resulted.  On  acidifying  with 


246  Wheeler  and  Johns. 

acetic  acid  mercaptan  was  evolved  and  a  granular  precipitate 
was  obtained.  This  was  filtered  and  dissolved  in  hot  water 
to  which  a  little  hydrochloric  acid  was  added.  The  hot  solution 
was  then  made  strongly  alkaline  with  ammonia  which  repre- 
cipitated  the  base.  This  treatment  removed  any  cytosine-5- 
carboxylic  acid  that  was  present,  the  acid  being  soluble  in 
ammonia.  The  best  yield  of  aminoamide  obtained  at  this 
point  was  about  75  per  cent  of  the  theory.  It  varied  con- 
siderably. For  analysis  the  aminoamide  was  purified  by 
recrystallizing  from  dilute  hydrochloric  acid.  The  hydro- 
chloride  was  then  dissolved  in  water,  with  the  aid  of  a  little 
hydrochloric  acid,  and  the  base  reprecipitated  with  ammonia, 
washed  thoroughly  with  water  and  alcohol,  and  finally  dried 
over  calcium  chloride.  It  did  not  lose  water  when  heated 
at  I20°-i30°  (Analyses  I.  II.  and  III.). 

When  we  first  obtained  this  material  attempts  were  made 
to  determine  nitrogen  by  Kjeldahl's  method  and  it  was  found 
that  neither  the  free  base  nor  any  of  its  salts  that  we  tried  gave 
results  agreeing  with  the  calculated.  The  figures  invariably 
came  several  per  cent  too  low.  It  appears  probable  that  the 
failure  to  obtain  correct  results  by  Kjeldahl's  method  was  due 
to  the  fact  that  the  weakly  basic  properties  of  the  compound 
permitted  the  escape  of  material  on  heating  the  sulphuric 
acid  solution.  This  might  have  escaped  unnoticed  if  we  had 
no  theory  to  check  the  results. 

I.  0.0763  gram  of  substance  gave  24.6  cc.  of  nitrogen  at 
22°  and  770  mm.  pressure. 

II.  0.2462  gram  of  substance  gave  0.0877  gram  of  H2O  and 
°-3575  gram  of  CO2. 

III.  0.1440  gram  of  substance  gave  0.0526  gram  of  H2O 
and  0.2093  gram  of  CO2. 

Calculated  for  Found. 

C6H602N4.  I.  II.  III.  IV. 

C          38.96          39.60          39-58  .../..  

3.89  4.00  3.90 

N          36.36  37-oo          36.38 

Cytosine-5-carboxamide  was  also  obtained  by  the  action  of 
concentrated  hydrochloric  acid  on  2-ethylmercapto-6-amino- 


Researches  on  Pyrimidines.  247 

pyrimidine-5-carboxamide.  One  gram  of  the  mercapto- 
aminoamide  was  evaporated  to  dryness  with  15  cc.  of  con- 
centrated hydrochloric  acid  on  the  steam  bath.  The  residue 
was  made  strongly  alkaline  with  ammonia.  This  extracted 
cytosine-5-carboxylic  acid  and  left  a  mixture  which  was 
boiled  with  alcohol.  Unaltered  mercaptoarninoamide  dis- 
solved. The  insoluble  material  was  purified  by  dissolving  in 
dilute  hydrochloric  acid  and  precipitating  with  an  excess  of 
ammonia  while  the  solution  was  hot.  This  gave  very  small, 
microscopic,  lenticular  crystals  that  did  not  show  signs  of 
melting  at  310°.  When  a  drop  of  nitric  acid  was  added  to 
the  hydrochloric  acid  solution  a  precipitate  of  the  nitrate  was 
formed.  (Analysis  IV.). 

Cytosine-5-carboxamide  is  almost  insoluble  in  water  and 
the  ordinary  organic  solvents.  It  dissolves  readily  in  cold 
alkalies,  but  it  is  almost  insoluble  in  ammonia.  It  does  not 
dissolve  in  acetic  acid.  It  dissolves  in  dilute  mineral  acids 
and  yields  beautiful  crystalline  salts  which  are  dissociated 
by  water.  The  aminoamide  is  a  weak  base.  Its  solubility 
in  alkali  is  in  accordance  with  the  presence  of  — NH — CO — 
groups.  The  free  aminoamide  prepared  from  the  brom  deriva- 
tive, when  obtained  by  precipitating  from  alkaline  solution 
by  acetic  acid  or  from  the  hydrochloric  acid  solution  with 
ammonia,  usually  appears  to  be  an  amorphous  powder.  Be- 
fore purifying  it  has  a  more  or  less  brownish  color.  Its  method 
of  separation  along  the  lines  of  stirring  indicates  a  crystalliza- 
tion but  the  crystals  are  too  minute  to  be  determined  under 
the  microscope. 

Action  of  Concentrated  Hydrochloric  Acid  on  Cy  to  sine- 5- 
carboxamide:  Cytosine-5-carboxylic  Acid. — The  amide  obtained 
from  the  bromamide  (0.6  gram)  was  boiled  with  50  cc.  of 
concentrated  hydrochloric  acid  for  about  five  minutes  and  the 
resulting  solution  evaporated  to  dryness  on  the  steam  bath. 
The  residue  dissolved  completely  in  ammonia.  On  acidifying 
with  acetic  acid  a  precipitate  of  cytosine-5-carboxylic  acid 
was  obtained.  This  decomposed  at  256°.  Analysis: 

Calculated  for 

CjHsOsNa.  Found. 

N  27.09  27.53 


248  Wheeler  and  Johns. 

This  acid  was  described  in  a  previous  paper.  It  should  be 
added  that,  like  the  amide,  it  is  almost  insoluble  in  water  and 
alcohol.  It  was  obtained  in  an  amorphous  condition.  When 
precipitated  from  its  solution  in  ammonia  by  acetic  acid  it 
separates  as  a  gelatinous  precipitate  which  is  difficult  to 
filter.  It  is  better  to  obtain  the  acid  by  evaporating  the 
ammonia  solution.  It  then  separates  as  a  finely  divided 
powder  which  is  readily  filtered.  It  is  also  readily  identified 
by  its  decomposing  point,  256°,  and  its  crystalline  hydro- 
chloride  which  contains  i  molecule  of  water  of  crystallization. 

Cytosine-5-carboxamide  Hydrochloride,  C5H6O2N4.HC1. — The 
base  dissolved  in  moderate  quantities  in  hot  dilute  hydro- 
chloric acid.  On  cooling,  the  hydrochloride  separated  al- 
most completely  in  clusters  of  colorless,  stout,  pointed  prisms 
which  did  not  have  a  definite  melting  point.  They  did  not 
lose  weight  on  heating  at  110°,  when  dried  over  calcium 
chloride.  When  heated  at  I4o°-i5o°  they  lost  their  lustre, 
hydrochloric  acid  being  slowly  given  off.  The  salt  was  dried 
at  110°  for  analysis: 

I.  0.0739  gram  of  substance  gave  19.0  cc.  of  N  at  22°  and 
768  mm. 

II.  0.0791  gram  of  substance  gave  0.0607  gram  of  AgCl. 

Calculated  for  Found. 

C6H602N4.HC1.  I.  II. 

N  29.40  29 .42  

Cl  18.64  l8-97 

Cytosine-5-carboxamide  Nitrate,  C5H6O2N4.HNO3. — This  is 
the  most  difficultly  soluble  and  characteristic  salt.  It  is 
formed  not  only  by  dissolving  the  amide  in  hot  nitric  acid  but 
also  on  adding  nitric  acid  to  solutions  of  other  salts  of  the  base. 

Cytosine-5-carboxamide  dissolved  very  slightly  in  hot  nitric 
acid.  On  cooling,  the  nitrate  separated  in  beautiful  truncated 
octahedrons.  When  nitric  acid  was  added  to  a  solution  of 
the  base  in  dilute  hydrochloric  acid  an  immediate  crystalline 
precipitate  of  the  nitrate  came  down.  It  then  formed  tufts 
of  short  hairs,  which  did  not  decompose  at  300°,  although  they 
sublimed  slowly  below  that  temperature.  They  did  not  lose 
weight  on  heating  at  115°.  Analysis: 


Researches  on  Pyrimidines.  249 

Calculated  lor 
C5H6O2N4.HNO3.  Found. 

N  32.26  32.05 

Cytosine-5-carboxamide  Sulphate,  (C5H6O2N4)2H2SO4. — A  solu- 
tion of  the  amide  was  made  in  hot  water  containing  about 
10  per  cent  sulphuric  acid.  The  sulphate  separated,  on  cool- 
ing, in  scales  with  a  pearly  lustre.  They  did  not  melt  at  300° 
and  no  loss  in  weight  took  place  on  heating  at  110°.  Analysis: 

0-0653  gram  of  substance  gave  0.0386  gram  BaSO4. 

Calculated  for 
(C6H6OaN4)2HtSO4.  Found. 

S  7.88  8. II 

Cytosine-5-carboxamide  Picrate,  C5H6O2N4.C6H2(NO2)3OH. — 
The  amide  was  dissolved  in  hot  water  to  which  a  few  drops  of 
hydrochloric  acid  had  been  added.  On  adding  an  aqueous 
solution  of  picric  acid  an  immediate  precipitate  was  formed. 
This  crystallized  from  an  aqueous  solution  of  picric  acid. 
It  dissociates  in  water  into  small,  yellow  prisms  that  began  to 
decompose  at  about  26o°-27o°.  The  salt  was  found  to  be 
anhydrous. 

I.  0.0531  gram  of  substance  gave  n.6  cc.  of  N  at  20°  and 
771  mm. 

II.  0.0967  gram  of  substance  gave  21.2  cc.  of  N  at  18°  and 
771  mm. 

Calculated  for  Found. 

CnH9O9N7.  I.  II. 

N  25.59  25.34  25.64 

The  papers  on  pyrimidines  which  have  been  published  from 
this  laboratory,  under  the  direction  of  Dr.  Treat  B.  Johnson 
and  the  writer,  have  appeared  in  two  journals.  Some  of 
these  papers  have  not  been  numbered  and  one  has  received 
an  incorrect  number,  there  being  two  twenty-first  papers. 
For  the  sake  of  reference  a  complete  list  of  these  papers  up  to 
the  end  of  the  year  1907  is  now  given.  The  papers  are  ar- 
ranged and  numbered  in  the  order  in  which  they  appeared. 
The  numbers  correspond  with  those  already  given  in  the 
literature,  with  the  exception  of  the  paper  which  has  been  in- 
correctly numbered.  By  referring  to  this  paper  as  the  twenty- 


250  Wheeler  and  Johns. 

fourth  the  order  then  remains  otherwise  undisturbed.     The 
following  is  a  complete  list  up  to  the  end  of  the  year  1907. 

1.  Researches    on    the    Cycloamidines:  Pyrimidine    Derivatives.     H. 
L.  Wheeler:  THIS  JOURNAL,  20,  481  (1898). 

2.  On  Some  Condensation  Products  of  the  Pseudothioureas :  Synthesis 
of  Uratil,   Thymine,  and  Similar  Compounds.     Henry  L.  Wheeler  and 
Henry  F.  Merriam:  THIS  JOURNAL,  29,  478  (1903). 

3.  Syntheses  of     Aminooxypyrimidines      having     the     Composition 
of    Cytosine:    2-Amino-6-oxypyrimidine    and    2-Oxy-6-aminopyrimidine. 
Henry  L.  Wheeler  and  Treat  B.  Johnson:  THIS  JOURNAL,,  29,  492  (1903). 

4.  On  Cytosine  or  2-Oxy-6-aminopyrimidine  from  Triticonucleic  Acid. 
Henry  L.  Wheeler  and  Treat  B.  Johnson:  THIS  JOURNAL,  29,  505  (1903). 

5.  5-Methylcytosine.     Henry    L.    Wheeler    and    Treat    B.    Johnson: 
THIS  JOURNAL,  31,  591  (1904). 

6.  Synthesis  of  2-Amino-5-methyl-6-oxypyrimidine.     Treat  B.  John- 
son and  Samuel  H.  Clapp:  THIS  JOURNAL,  32,  130  (1904). 

7.  2-Oxy-4,6-diaminopyrimidine.     Henry  L.  Wheeler  and  George  S. 
Jamieson:     THIS  JOURNAL,  32,  342  (1904). 

8.  The  Structure  of  Some  Substitution  Products.     Henry  L.  Wheeler 
and  H.  Stanley  Bristol:  THIS  JOURNAL,  33,  437  (1905). 

9.  The  Action  of  Potassium  Thiocyanate  upon  Some   Imidechlorides. 
Henry  L.  Wheeler  and  H.  Stanley  Bristol:  THIS  JOURNAL,  33,  448  (1905). 

10.  The  Action  of  Aqueous  and  Alcoholic  Ammonia  and  Aniline  on 
Some  Halogen-  and  Mercaptopyrimidines.     Treat  B.  Johnson  and  Carl 
O.  Johns:  THIS  JOURNAL,  34,  176  (1905). 

11.  2-Ethylmercapto-5-amino-6-oxypyrimidine.     Treat     B.     Johnson: 
THIS  JOURNAL,  34,  191  (1905). 

12.  2,5-Diamino-6-oxypyrimidine.     Treat    B.    Johnson    and    Carl    O. 
Johns:  THIS  JOURNAL,  34,  554  (1905). 

13.  Some    lodopyrimidines:    5-Iodocytosine.     Treat  B.    Johnson    and 
Carl  O.  Johns:  /.  Biol.  Chem.,  I,  305  (1906). 

14.  On  Methods  of  Synthesizing  Isobarbituric  Acid  and  5-Oxycytosine. 
Treat  B.  Johnson  and  Elmer  V.  McCollum:    J.  Biol.  Chem.,  i,  437  (1906). 

15.  The    Action    of     Potassium     Thiocyanate     upon     Imidechlorides. 
Treat  B.  Johnson  and  Elmer  V.  McCollum:  THIS  JOURNAL,  36,  136  (1906). 

1 6.  The  Formation  of  Purines  from  Ureapyrimidines.     Treat  B.  John- 
son and  Elmer  V.  McCollum:  THIS  JOURNAL,  36,  149  (1906). 

17.  5-Nitrocytosine  and  its  Reduction  to  2-Oxy-5,6-diaminopyrimidine. 
Treat  B.  Johnson,  Carl  O.  Johns,  and  Frederick  W.  Heyl:  THIS  JOURNAL, 
36,  160  (1906). 

1 8.  5-Ethylcytosine.     Treat    B.    Johnson    and   George    A.    Menge:  /. 
Biol.  Chem.,  2,  105  (1906). 

19.  Synthesis  of  Uracil-5-carboxylic  Acid.     Henry  L.  Wheeler,  Treat 
B.  Johnson,  and  Carl  O.  Johns:  THIS  JOURNAL,  37,  392  (1907). 

20.  Some   Condensation   Products   of   a   Substituted   Pseudothiourea: 


Researches  on  Pyrimidines.  251 

Synthesis  of  i -Methyl uracil.     Treat  B.  Johnson  and  F.  W.  Heyl:  THIS 
JOURNAL,  37,  628  (1907). 

21.  On  a  Color  Test  for  Uracil  and  Cytosine.     Henry  L.  Wheeler  and 
Treat  B.  Johnson:  /.  Biol.  Chem.,  3,  183  (1907). 

22.  On  Some  Salts  of  Cytosine,  Isocytosine,  6-Aminopyrimidine,  and 
6-Oxypyrimidine.     Henry  L.  Wheeler:  /.  Biol.  Chem.,  3,  285  (1907). 

23.  Uracil-4-carboxylic  Acid.     Henry  L.  Wheeler:  THIS  JOURNAL,  38, 
358  (1907). 

24.  The    Action  of  Methyl  Iodide  on  2-Anilino-6-oxypyrimidine    and 
the  Synthesis  of  2-Anilinopyrimidine.     Treat  B.  Johnson  and  Frederick 
W.  Heyl:  THIS  JOURNAL,  38,  237  (1907). 

25.  Synthesis  of   Thymine-4-carboxylic  Acid.     Treat   B.   Johnson:  /. 
Biol.  Chem.,  3,  299  (1907). 

26.  Synthesis  of  Cytosine-5-carboxylic  Acid.     Henry  L.  Wheeler  and 
Carl  O.  Johns:  THIS  JOURNAL,  38,  594  (1907). 

27  Synthesis  of  Thymine-5'-carboxylic  Acid.  (Uracil-5-acetic  Acid). 
Treat  B.  Johnson  and  Carl  Frank  Speh:  THIS  JOURNAL,  38,  602  (1907). 

28.  Synthesis  of  4-Methyluracil-5-acetic  Acid.  Treat  B.  Johnson  and 
Frederick  W^  Heyl:  THIS  JOURNAL,  38,  659  (1907). 

NEW  HAVEN,  CONN., 
March,  1908. 


[.Reprinted  from  the  American  Chemical  Journal,  Vol,  XI,. 
No.  4.    October,  1908.] 


CLX.— RESEARCHES    ON    PYRIMIDINES: 
SYNTHESIS   OF  4-METHYLCYTOSINE. 

[THIRTY-SEVENTH  PAPER]. 

BY  CARL  O.  JOHNS. 

There  are  two  methyl  derivatives  of  cytosine  having  the 
methyl  group  attached  to  carbon.  Of  these,  5-methylcy- 
tosine  (Formula  I.)  has  been  described  in  the  fifth  paper  of 


Researches  on  Pyrimidines.  349 

this  series,1  while  a  description  of  the  synthesis  and  properties 
of  4-methylcytosine  (V.)  will  be  given  in  the  following  pages. 

Acetoacetic  ester  condenses  readily  in  an  aqueous  solution 
of  sodium  hydroxide  with  pseudoethylthiourea  hydrobromide 
to  give  an  excellent  yield  of  2-ethylmercapto-4-methyl-6-oxy- 
pyrimidine  (II.)-  This  compound  has  been  prepared  by 
List2  but  his  method  requires  several  days,  and,  calculating 
from  the  weight  of  acetoacetic  ester  used,  the  yields  are  only 
about  one-half  as  great  as  those  obtained  by  the  method 
here  described. 

When  2-ethylmercapto-4-methyl-6-oxypyrimidine  is  boiled 
with  phosphorus  oxy  chloride  it  yields  2-ethylmercapto- 
4-methyl-6-chlorpyrimidine  (III.)-  When  heated  in  a  sealed 
tube  at  I4o°-i5o°  with  alcoholic  ammonia  the  chlorine  in 
this  compound  is  replaced  by  an  amino  group  and  2-ethyl- 
mercapto-4-methyl-6-aminopyrimidine  (IV.)  is  obtained.  This 
is  readily  converted  into  4-methylcytosine  (V.)  by  digest- 
ing with  concentrated  hydrochloric  acid  and  precipitating 
the  base  with  a  slight  excess  of  ammonium  hydroxide. 

The  chloride  (III.)  reacts  more  readily  with  alcoholic  so- 
dium ethylate  than  it  does  with  alcoholic  ammonia.  Action 
takes  place  at  room  temperature.  Sodium  chloride  separates 
and  2-ethylmercapto-4-methyl-6-ethoxypyrimidine  (VI.)  is 
formed. 

4-Methylcytosine  can  easily  be  distinguished  from  5-methyl- 
cytosine.  It  does  not  melt  at  310°,  while  5-methylcytosine 
melts  with  effervescence  at  270°.  It  is  far  less  soluble  in 
water  than  is  5-methylcytosine.  Moreover,  4-methylcy- 
tosine crystallizes  from  water  in  long,  anhydrous  prisms, 
while  5-methylcytosine  gives  flat  prisms  containing  one-half 
molecule  of  water. 

4-Methylcytosine  gives  a  very  characteristic  basic  hydro- 
chloride  containing  3  molecules  of  base  to  i  molecule  of  hy- 
drogen chloride  while  5-methylcytosine  under  similar  con- 
ditions gives  a  hydrochloride  containing  2  molecules  of  base 
to  one  of  acid. 

1  Wheeler  and  Johnson:  THIS  JOURNAL,  31,  591  (1904). 

2  Ann.  Chem.  (Liebig),  236,  14  (1886). 


350 


Johns. 


When  crystallized  from  concentrated  solutions  of  the  com- 
mon acids,  4-methylcytosine  gives  a  series  of  normal  salts. 

4-Methylcytosine  has  been  used  for  the  preparation  of 
some  purine  derivatives  to  be  described  in  another  paper. 


N  =  CNH2 

I         I 
OC       C.CH, 

I         II 

HN  — CH 

I. 

N  ==  CNH2 

I         I 
OC       CH 

I         II 

HN  — C.CH8 
V. 


HN  — CO 

I  I 
C2H6SC       CH 

II  II 

N  — C.CH3 
II. 


N^CCl 

I         I 
C2H6SC       CH 


N  —  C.CH, 

III. 


/ 


N  =  CNHa 

I  I 
C2H5SC       CH 

II  II 

N  —  C.CH3 
IV. 

EXPERIMENTAL  PART. 


N  =  COC3H5 

C2H6SC       CH 

II        II 
N  — C.CH, 
VI. 


HN  — CO 


2-Ethylmercapto-4-methyl-6-oxypyrimidine,  C2H5SC        CH     . 

N  — C.CH, 

— List1  prepared  this  compound  by  heating  2-thio-4-methyl- 
6-oxypyrimidine  with  ethyl  iodide  in  the  presence  of  sodium 
ethylate.  It  can  be  obtained  more  easily  and  in  better  yields 
by  condensing  pseudoethylthiourea  hydrobromide  with  aceto- 
acetic  ester  in  an  aqueous  solution  of  sodium  hydroxide. 
This  condensation  is  very  smooth  and  the  yields  range  from 
80  to  90  per  cent  of  the  theoretical  quantity. 

Ninety-three  grams  of  pseudoethylthiourea  hydrobromide 
are  dissolved  in  100  cc.  of  water  and  this  solution  is  mixed 
with  65  grams  of  acetoacetic  ester.  To  this  mixture  is  slowly 
added  a  solution  of  40  grams  of  sodium  hydroxide  in  80  cc. 
of  water.  Condensation  takes  place  at  once,  but  to  insure 
complete  reaction  the  mixture  is  allowed  to  stand  at  room 
temperature  overnight.  When  the  resulting  clear  solution 

i  Ann.  Chem.  (Liebig),  236,  14  (1886). 


Researches  on  Pyrimidines.  351 

is  acidified  with  acetic  acid  about  75  grams  of  2-ethylmer- 
capto-4-methyl-6-oxypyrimidine    are    obtained.     When    crys- 
tallized from  dilute  alcohol  it  melts  at  i44°-i45°  and  pos- 
sesses all  the  properties  of  List's  compound. 
Analyses  (Kjeldahl) : 

Calculated  for  Found. 

C7H10ON2S.  I.  II. 

N  16.47  16.49  16.52 


N  =  CC1 

I  | 

2-Ethylmercapto-4-methyl-6-chlorpyrimidine,  C2H5SC       CH 


N  —  CCH$ 

—  Twenty  grams  of  2-ethylmercapto-4-rnethyl-6-oxypyrimi- 
dine  were  heated  with  60  cc.  of  phosphorus  oxychloride  in 
an  oil  bath  kept  at  I3o°-i35°  until  hydrogen  chloride  was 
no  longer  evolved.  The  excess  of  phosphorus  oxychloride 
was  removed  under  diminished  pressure  and  the  resulting 
thick  oil  was  poured  on  cracked  ice.  The  chloride  was  ex- 
tracted with  ether  and  dried  over  calcium  chloride.  When 
the  ether  was  evaporated  a  clear,  red  oil  remained.  This 
boiled  at  142°  at  15  mm.  pressure.  The  yield  of  pure  chlor- 
ide was  about  75  per  cent  of  the  calculated  quantity.  This 
chloride  is  very  stable  towards  water  and  alcohol. 
Analyses  (Kjeldahl)  : 

Calculated  for  Found. 

I.  II. 


N  14-85  14-71  15-09 

2-Ethylmercapto-4-methyl-6-ethoxypyrimidine, 
N  =  COC,H5 

C2H5SC       CH        .  —  An  ether   solution   of    2-ethylmercapto- 

'    II        II 
N  —  CCH3 

4-methyl-6-chlorpyrimidine  was  added  to  alcohol  contain- 
ing an  excess  of  sodium,  calculating  from  the  chloride.  An 
immediate  reaction  took  place  with  the  liberation  of  heat. 


352  Johns. 

The   excess   of    alcohol   was   evaporated,    and,    after   adding 
water,  the  oil  was  shaken  out  with  ether  and  dried  over  cal- 
cium chloride.     When  the  ether  was  evaporated  an  oil  re- 
mained.    This  boiled  at  154°  at  20  mm.  pressure. 
Analyses  (Kjeldahl): 

Calculated  for  Found. 

C9H14ON2S.  I.  II. 

N  14-14  14.08  14-43 

2-Ethylmercapto-4-methyl-6-aminopyrimidine, 


I  I 

C,H5SC       CH     .  —  Alcoholic    ammonia    does    not    react    at 

II  II 

N  —  CCH, 

room  temperature  with  2-ethylmercapto-4-methyl-6-chlorpyr- 
imidine.  Sixteen  grams  of  the  chloride  were  heated  in  a  sealed 
tube  for  4  hours  at  I4o°-i5o°  with  about  75  cc.  of  alcoholic 
ammonia  saturated  at  o°.  The  tube,  wheen  cooled,  was 
lined  with  ammonium  chloride  and  crystals  of  the  new  amino 
compound.  The  reaction  was  very  smooth  and  the  alcohol 
remained  colorless.  After  evaporating  to  dryness,  the  resi- 
due was  washed  with  cold  water  and  recrystallized  from  di- 
lute alcohol.  The  crystals  melted  at  ii5°-n6°  to  a  clear 
oil.  They  have  a  tetrahedral  outline  and  show  a  great  ten- 
dency to  twin.  They  are  easily  soluble  in  cold  alcohol  and 
acetic  acid,  moderately  soluble  in  cold  benzene,  and  diffi- 
cultly soluble  in  boiling  water. 
Analyses  (Kjeldahl)  : 

Calculated  for  Found. 

C7HUN3S.  I.  II. 

N  24.85  24.83  25.07 

N  =  CNH3 

I         I 
4-Methylcytosine,    OC       CH       .  —  When    2-ethylmercapto- 

I         II 
HN  —  CCHS 

4-methyl-6-aminopyrimidine  is  evaporated  with  concentrated 
hydrochloric  acid  ethyl  mercaptan  is  evolved  and  an  almost 


Researches  on  Pyrimidines.  353 

theoretical  yield  of  4-methylcytosine  monohydrochloride  is 
obtained.  The  base  is  obtained  from  this  salt  by  adding 
an  excess  of  ammonium  hydroxide.  4-Methylcytosine  crys- 
tallizes from  water  in  anhydrous,  slender,  brittle  prisms. 
These  crystals  do  not  melt  at  310°,  but  decompose  slowly 
without  effervescence  at  higher  temperatures.  4-Methylcytosine 
is  moderately  soluble  in  boiling  water.  At  24°,  0.36  gram  is 
dissolved  by  100  cc.  of  water.  It  is  soluble  in  cold  aqueous 
ammonia  and  in  cold  acetic  acid. 
Analyses  (Kjeldahl): 

Calculated  for  Found. 

C6H7ON3.  I.  II. 

N  33-6o  33.52  33.39 

4-Methylcytosine  Monohydrochloride,  C5H7ON3.HC1. — This 
salt  is  obtained  when  2-ethylmercapto-4-methyl-6-amino- 
pyrimidine  is  digested  with  concentrated  hydrochloric  acid. 
It  is  also  formed  by  crystallizing  4-methylcytosine  from  20 
per  cent  hydrochloric  acid.  It  is  moderately  soluble  in  hot 
hydrochloric  acid  and  separates  on  cooling  in  blunt,  flat 
prisms  with  a  hexagonal  appearance.  When  dried  over  potas- 
sium hydroxide  it  does  not  lose  water  at  110°.  In  a  capillary 
tube  it  begins  to  shrivel  at  about  280°  and  decomposes  slowly 
above  300°. 

Analyses : 

Calculated  for  Found. 

C5H7ON3.HC1.  I.  II. 

N                 26.00                26.10                26.09 
Cl  21.98  21.81  

The  anhydrous  monohydrochloride  of  4-methylcytosine  is 
also  obtained  unaltered  when  its  aqueous  solution  is  saturated 
with  hydrogen  chloride  and  evaporated  in  a  desiccator.  The 
crystals  thus  obtained  did  not  lose  weight  at  125°. 

Analysis : 

Calculated  for 

C6H7ONVHC1.  Found. 

Cl  2 i . 98  2 i . 95 

4-Methylcytosine    Basic     Hydrochloride,     (C5H  7ON3)3.HC1.— 
>uch  a  salt  was  formed  when  a  hot  aqueous  solution  of  0.25 


354  J°hns> 

gram  of  the  base  was  mixed  with  an  aqueous  solution  of  0.32 
gram  of  the  monohydrochloride.  The  basic  salt  separated 
in  scales  with  a  pearly  lustre.  These  began  to  shrivel  at  about 
270°  and  turned  brown  above  280°  but  did  not  melt  at  310°. 
These  crystals  lost  weight  when  dried  at  130°-  140°,  but  at- 
tempts to  determine  water  of  crystallization  gave  results 
that  differed  widely,  but  indicated  that  one  molecule  of  water 
was  probably  present.  The  dried  salt  contained  3  molecules 
of  the  base  and  i  molecule  of  hydrogen  chloride.  This  same 
salt  was  obtained  when  equal  weights  of  the  base  and  mono- 
hydrochloride were  recrystallized  from  water. 
Analyses  of  the  dried  salt: 

Calculated  for  Found. 

(CsHTON3)3.HCI.  I.  II.  III. 

N  30.61  ----  30.26  ---- 

Cl  8.62  8.51  .....  8.49 

4-Methylcytosine  Nitrate,  C5H7ON3.HNO3.—  One-half  gram  of 
4-methylcytosine  was  crystallized  from  10  cc.  of  25  per  cent 
nitric  acid.  The  salt  separated  in  round  clusters  of  blunt 
prisms.  It  did  not  contain  water  of  crystallization. 

0.0983  gram  of  substance  gave  25.2  cc.  of  moist  nitrogen 
at  18°  and  770  mtn.  pressure. 

Calculated  for 

Found. 


N  29.79  29.94 

4-Methylcytosine  Siilphate,  (C5H7ON3)2.H2SO4.H2O.—  When 
4-methylcytosine  was  crystallized  from  25  per  cent  sulphuric 
acid,  two  molecules  of  the  base  united  with  one  molecule  of 
sulphuric  acid  to  form  a  normal  sulphate  containing  one  mole- 
cule of  water  of  crystallization.  The  crystals  were  large, 
flat  prisms  tjiat  did  not  lose  water  at  110°,  but  lost  one  mole- 
cule of  water  slowly  at  i6o°-i7o°. 

Analyses: 

Calculated  for  Found. 

(C5H7ON3)2.H3S04.H2O.       I.  II.  HI. 

H20     4.91      ....      4-83 

N      22.95     22.79      ••••     22.82 

S  8.74  ....  8-88 


Researches  on  Pyrimidines.  355 

4-Methylcytosine  Picrate,  C5H7ON3.CCH2(NO2)3OH.— When 
an  aqueous  solution  of  picric  acid  is  added  to  a  solution  of 
4-methylcytosine,  an  immediate  precipitate  is  obtained. 
This  picrate  is  difficultly  soluble  in  hot  water  and  crystal- 
lizes in  beautiful,  yellow  needles  that  turn  brown  at  about 
265°  and  decompose  slowly  above  that  temperature. 

0.0858  gram  of  substance  gave  17.3  cc.  of  moist  nitrogen 
at  18°  and  772  mm.  pressure. 


N 

NEW  HAVEN,  CONN., 
May,  1908. 


Calculated  for 
C5H7ON3.C6H2(N02)aOH. 

23-73 


Found. 
23.65 


[Reprinted  from  the  American  Chemical  Journal,  Vol.  XI,. 
No.  5.    November,  1908.] 


[Contributions  from  the  Sheffield  Laboratory  of  Yale  University.] 

CLXL— RESEARCHES  ON  PYRIMIDINES: 

SYNTHESES  OF  SOME  BENZYL  DERIVATIVES 

OF  URACIL  AND  THYMINE. 

[THIRTY-EIGHTH  PAPER.] 

BY  TREAT  B.  JOHNSON  AND  JOHN  H.  DERBY,  JR. 

In  order  to  determine  the  structure  of  some  new  nitrogen 
derivatives  of  uracil  and  thyrnine  it  was  essential  to  have 
knowledge  of  some  characteristic  nitrogen-alkyl  derivatives  of 


Researches  on  Pyrimidines. 


445 


these  pyrimidines  of  known  constitution.  The  only  nitrogen- 
alkyl  derivatives  of  uracil  and  thymine  mentioned  in  the  litera- 
ture are  1,3-dimethylthymine1  and  the  methyl  and  ethyl  com- 
pounds, which  have  been  described  in  previous  papers  from 
this  laboratory.2  These  alkyl  pyrimidines  were  not  suitable 
for  our  work  on  account  of  their  solubility,  and  difficulty  of 
isolation  when  accompanied  by  impurities.  Furthermore, 
3-methyluracil  has  not  been  synthesized. 

With  the  anticipation  that  the  nitrogen-benzyl  derivatives 
of  uracil  and  thymine  might  be  found  to  be  more  insoluble,  and 
suitable  for  our  work,  we  undertook  this  investigation.  We 
shall  describe  in  this  paper  the  methods  of  preparation  and 
the  properties  of  i-benzyluracil,  I.,  3-benzyluracil,  II.,  i-benzyl- 
thymine,  III.,  and  3-benzylthymine,  IV. 

NH CO 

I 
CH 

II 
CH 


Johnson  and  Heyl3  showed  that  methyl  iodide  reacts  with 
2-ethylmercapto-6-oxypyrimidine,4  in  presence  of  alkali,  giving 
i-methyl-2-ethylmercapto-6-oxypyrimidine,  V.  They  did  not 
observe  the  formation  of  the  isomeric  2-ethylmercapto-3- 
methyl-6-oxypyrimidine,  VI.  Wheeler  and  Liddle5  observed, 
on  the  other  hand,  that  ethyl  chloracetate  reacts  with  this 
mercaptopyrimidine,  giving  2-ethylmercapto-3-ethylacetate-6- 

1  Steudel:  Z.  physiol.  Chem.,  30,  539. 

*  Johnson  and  Heyl:  THIS  JOURNAL,  87,  628;  Johnson  and  Clapp:  J.  Biol.  Chem. 
5,49. 

3  Loc.  cit. 

4  THIS  JOURNAL,  29,  478.  492. 
8  J.  Am.  Chem.  Soc.,  30,  1152. 


446  Johnson  and  Derby,  Jr. 

oxypyrimidine,  VII.,  instead  of  the  isomeric  mercaptopyrimi- 
dine,  VIII. 

CH3N CO  N CO 

KSC  CH  C2H5SC  CH 

i  II 

CH3N CH 

VI. 


H 
VII. 

We  now  find  that  benzyl  chloride  reacts  with  2-ethylmer- 
capto-6-oxypyrimidine  in  presence  of  alkali,  giving  a  mixture 
of  two  isomeric  mercaptopyrimidines  melting  at  77°  and  139.° 
They  were  converted  quantitatively  into  the  corresponding 
benzyluracils  melting  at  175°  and  173°,  respectively,  by 
hydrolysis  with  hydrochloric  acid. 

The  structures  of  the  benzyluracils  and  incidentally  of  the 
mercaptopyrimidines  were  established  in  the  following  manner : 
The  benzyluracil  melting  at  173°  reacted  with  methyl  iodide, 
giving  i -methyl-3 -benzyluracil,  XVI.  This  same  pyrimidine 
was  also  obtained  by  the  action  of  benzyl  chloride  on  i-methyl- 
uracil,1  XVIII.  This  benzyl  derivative  is  therefore  to  be 
represented  as  3 -benzyluracil,  XIII.,  and  the  isomer,  melting 
at  175°,  as  i -benzyluracil,  XII.  The  mercaptopyrimidines, 
melting  at  77°  and  139°,  are  therefore  to  be  assigned  the  struc- 
tural formulas  IX.  and  X.,  viz.,  i-benzyl-2-ethylmercapto-6- 
oxypyrimidine  and  2-ethylmercapto-3-benzyl-6-oxypyrimidine, 
since  they  are  converted  into  i -benzyluracil,  XII.,  and  3- 
benzyluracil,  XIII.,  respectively,  by  hydrolysis  with  acids. 

2-Ethylmercapto-5-brom-6-oxypyrimidine2  reacted  with  ben- 
zyl chloride,  giving  an  excellent  yield  of  2-ethylmercapto-3- 
benzyl-5-brom-6-oxypyrimidine,  XI.  This  was  converted 

1  Johnson  and  Heyl:  Loc.  ctt. 

2  THIS  JOURNAL,  31,  603. 


Researches  on  Pyrimidines.  447 

quantitatively  into  3-benzyl-5-bromuracil,  XIV.,  by  hydrolysis 
with  hydrochloric  acid.  The  same  pyrimidine  was  also  formed 
by  the  action  of  bromine  on  3-benzyluracil,  XIII.  i-Methyl-3- 
benzyl-5-bromuracil,  XVII.,  was  formed  by  treatment  of 
3-benzyl-5-bromuracil,  XIV.,  with  methyl  iodide,  in  presence 
of  alkali,  and  also  by  the  action  of  bromine  on  i-methyl-3- 
benzyluracil,  XVI. 

3-Benzyluracil,  XIII.,  reacted  with  cold,  fuming  nitric  acid, 
giving  a  dinitropyrimidine  which  we  have  provisionally  repre- 
sented as  3-/>-nitrobenzyl-5-nitrouracil,  XV. 

Johnson  and  Clapp1  observed  that  2-ethylmercapto-5- 
methyl-6-oxypyrimidine,  XIX.,  reacted  with  methyl  iodide, 
in  presence  of  alkali,  giving  about  equal  proportions  of  1,5- 
dimethyl-2-ethylmercapto-6-oxypyrimidine,  XX.,  and  2-ethyl- 
mercapto-3,5-dimethyl-6-oxypyrimidine,  XXI.  We  now  find 
that  benzyl  chloride  reacts  with  this  mercaptopyrimidine,  under 
the  same  conditions,  giving  i-benzyl-2-ethylmercapto-5-methyl- 
6-oxypyrimidine,  XXII.,  melting  at  72°,  and  2-ethylmercapto- 
3-benzyl-5-methyl-6-oxypyrimidine,  XXIV.,  melting  at  121°- 
122°.  These  pyrimidines  were  converted  quantitatively  into 
i-benzylthymine,  XXIII.,  melting  at  205°,  and  3-benzyl- 
thymine,  XXVI.,  melting  at  i59°-i6o°,  by  hydrolysis  with  con- 
centrated hydrochloric  acid. 

The  structures  of  these  four  pyrimidines  was  determined  by 
the  behavior  of  the  two  benzylthymines  towards  diazobenzene- 
sulphonic  acid.  Johnson  and  Clapp2  have  shown  in  a  recent 
paper  that  this  reagent  can  be  used  to  distinguish  between 
i-  and  3-alkyl  derivatives  of  uracil  and  thymine.  They  ob- 
served, for  example,  that  i-alkyl  derivatives  of  these  pyrimi- 
dines reacted  with  this  reagent,  giving  red  colored  solutions. 
The  isomeric  3-alkylpyrimidines,  on  the  other  hand,  did  not 
react  with  the  diazo  acid  with  the  formation  of  red  colors.  We 
now  find  that  the  benzylthymine,  melting  at  205°,  reacts  with 
the  sulphonic  acid,  giving  a  brilliant  red  solution,  indicating  that 
it  is  a  i -benzyl  thymine  as  represented  by  formula  XXIII. 
The  isomer  gave  no  color  with  the  sulphonic  acid  and  therefore 

*  Loc.  tit. 

2  J.  Biol.  Chem.f  Vol.  5. 


448 


Johnson  and  Derby,  Jr. 


p     pq      W 
0—0=0 


W     o 


W     W 


=0— 


__ 


O     W     W 

0—0=0 


p 

0—0= 


g-8-i 


Researches  on  Pyrimidines. 


449 


a_|  «  :;:;;    8-3=3,        §-M, 

B       ..  IB     lias 

£ 

=^~& 

2«  w               w"        w1 

*     W                               h 

n    rl                   o           o 

PI  °               r?  «"                   M 

•"         '  ;-:'  -     3  111  S    5 

8-l-g.       ?J=sd       3-ts, 

M 

S                               Q 

g_0=iR           i-8-gH          §-8-i* 

3                    w 

w 

W                           ci 

q» 

cJ                        5 

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1     HI      I 

W*    cThj 

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C 

3-S=S      ;    ;!    8- 

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a                           °x/:z:o 
o    W                  o    V    W 
-0=^0                   o—  o—  o 

8                   i     g     J 

i 

i 

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^,—  ^=^                          ^,"" 

•g,  z           K  °  §• 

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o: 

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* 

450  Johnson  and  Derby,  Jr. 

is  to  be  assigned  formula  XXVI.  The  corresponding  mer- 
captopyrimidines  melting  at  72°  and  I2i°-i22°  must  therefore 
be  represented  by  formulas  XXII.  and  XXIV.,  respectively. 

It  is  of  interest  to  note  here  that  the  structures  of  the  above 
benzyluracils,  XII.  and  XIII.,  can  also  be  determined  by  means 
of  the  diazo  reagent.  i-Benzyluracil,  XII.,  reacted  with  the 
acid,  in  presence  of  sodium  hydroxide,  giving  a  permanent  red 
color,  while  its  isomer,  XIII.,  did  not  give  a  red  color  under  the 
same  conditions. 

i -Methyl-3 -benzyl  thy  mine,  XXVII.,  was  formed  by  the 
action  of  methyl  iodide  on  3 -benzyl thymine,  XXVI.  When 
the  latter  pyrimidine,  XXVI.,  was  dissolved  in  cold,  fuming 
nitric  acid  of  density  1.5  it  was  converted  into  a  hydropyrimi- 
dine,1  XXV.,  viz.,  3-/>-nitrobenzyloxynitrohydrothymine. 

The  four  pyrimidines,  i-benzyluracil,  3-benzyluracil,  i- 
benzylthymine,  and  3-benzylthymine,  are  characterized  by 
their  insolubility  in  cold  water.  3~Benzyluracil  and  3-benzyl- 
thymine are  less  soluble  in  water  than  uracil  and  thymine. 
They  all  crystallize  from  hot  water  without  water  of  crystal- 
lization. They  are  weak  acids  and  can  be  heated  above  their 
melting  points  without  decomposition. 

EXPERIMENTAL,  PART. 

C6H5CH2N CO 

i-Benzyl-2-ethylmercapto-6-oxypyrimidine,     C2H5SC         CH. 

N CH 

— Fifteen  grams  of  2-ethylmercapto-6-oxypyrimidine  and  5.4 
grams  of  finely  pulverized  potassium  hydroxide  were  dissolved 
in  about  75  cc.  of  boiling  absolute  alcohol.  Twelve  and  two- 
tenths  grams  of  benzyl  chloride  were  then  added  and  the  solu- 
tion heated  on  the  steam  bath  until  it  gave  no  alkaline  reaction 
with  moist  turmeric  paper  (about  4  hours).  After  cooling, 
the  undissolved  potassium  chloride  was  filtered  off  and  the 
alcohol  removed  by  evaporation  on  the  steam  bath.  We  ob- 
tained a  crystalline  product  which  was  triturated  with  50  cc. 
of  a  5  per  cent  solution  of  sodium  hydroxide  to  remove  un- 

1  Johnson:  THIS  JOURNAL,  40,  19;  J.  Biol.  Chem.,  4,  407. 


Researches  on  Pyrimidines.  451 

altered  pyrimidine  and  potassium  chloride.  When  the  alkaline 
solution  was  acidified  with  acetic  acid  we  recovered  1.7  grams 
of  2-ethylmercapto-6-oxypyrimidine.  The  crystalline  material, 
insoluble  in  sodium  hydroxide,  was  then  extracted  thoroughly 
with  an  excess  of  ether  and  the  insoluble  material  saved  (see 
3-benzyl  derivative  below).  When  the  ether  solution  was 
allowed  to  evaporate  we  obtained  some  oil  and  about  3.0  grams 
of  crystalline  material  which  melted  at  65°-7o°  to  a  clear  oil 
with  no  effervescence.  The  oil  gradually  assumed  a  crystalline 
form  on  standing.  The  pyrimidine  separated  from  alcohol  in 
well-developed  prisms  melting  at  77°.  The  weight  of  one 
crystal,  which  was  selected  for  analysis,  was  0.3+  gram. 
Analysis  (Kjeldahl)  : 

Calculated  for 
CisHuONaS.  Found. 

N  11.38  11.63 

2-Ethylmercapto-3-benzyl-6-oxy  pyrimidine, 

if      "l 
C2H5SC          CH.—  The  weight  of  the  crude  3-benzyl  deriv- 

CCH5CH2.N  -  CH 

ative,  insoluble  in  ether,  in  the  above  experiment,  was  1  1  .  i  grams, 
corresponding  to  5  1  per  cent  of  the  calculated.  The  pyrimidine 
is  soluble  in  warm  benzene,  acetone,  alcohol,  very  soluble  in 
chloroform,  and  practically  insoluble  in  cold  ether  and  ligroin. 
It  is  difficultly  soluble  in  hot  water  and  crystallizes  in  long, 
slender  prisms,  and  hexagonal  prisms  or  flat  tables  melting  at 
139°  to  an  oil.  This  melting  point  was  not  raised  by  recrys- 
tallization  from  benzene. 
Analysis  (Kjeldahl)  : 

Calculated  for  Found. 

I.  II. 


N  11-38  11.58  ii.  61 

2-Ethylmercapto-  3-benzyl-  5~brom-6-oxy  pyrimidine, 
N  ---  CO 

II  I 

C2H5S.C  CBr.  —  This  compound  was  obtained  when  5.0 

i       ii 

C,H6CH2N- 


452  Johnson  and  Derby,  Jr, 

grams  of  2-ethylmercapto-5-brom-6-oxypyrimidine1  were  heated 
in  absolute  alcohol,  for  4  to  5  hours,  with  the  required  propor- 
tions of  potassium  hydroxide  and  benzyl  chloride.  After 
filtration  from  the  undissolved  potassium  chloride  and  evapo- 
ration of  the  alcohol  we  obtained  a  semisolid  substance  which 
immediately  solidified  when  washed  with  ether.  The  yield  was 
4.2  grams,  corresponding  to  60.0  per  cent  of  the  calculated. 
The  pyrimidine  is  difficultly  soluble  in  water  and  separates 
from  a  hot,  aqueous  solution  in  needles  melting  at  129°  to  a 
clear  oil.  Analysis  (Kjeldahl) : 

Calculated  for 

Ci3Hi8ON2BrS.  Found. 

N                                8.62  9.0 

C8H5CH2.N CO 

i-Benzyluracil,  CO        CH. — A   quantitative  yield 

NH CH 

of  this  pyrimidine  was  obtained  when  3.0  grams  of  the  correspond- 
ing 2-mercaptopyrimidine  were  dissolved  in  150  cc.  of  con- 
centrated hydrochloric  acid  and  the  solution  evaporated  to 
dryness.  It  crystallizes  from  hot  water  in  prismatic  crystals 
melting  at  175°  to  a  clear  oil.  It  did  not  contain  water  of 
crystallization.  When  mixed  with  the  isomeric  3-benzyluracil 
(see  below)  melting  at  173°,  the  fusion  point  was  lowered  to 
I40°-i55°.  Thepyrimidine  reacted  with  diazobenzenesulphonic 
acid,  in  presence  of  alkali,  giving  a  red  colored  solution.  Anal- 
ysis (Kjeldahl) : 

Calculated  for 

CuHi0O2N2.  Found. 

N  13.86  14.1 

NH CO 

I  I 

3-Benzyluracil,  CO        CH. — This   pyrimidine   was 

I  II 

C6H5CH2.N CH 

prepared  by  digesting  6.7  grams  of  2-ethylmercapto-3-benzyl-6- 
oxypyrimidine  with  concentrated  hydrochloric  acid  for  5  to  6 

1  Wheeler  and  Johnson:  THIS  JOURNAL,  31,  603. 


Researches  on  Pyrimidines.  453 

hours.  The  yield  was  5.5  grams  or  96  per  cent  of  the  theoretical. 
It  crystallizes  from  alcohol  in  stout  prisms  melting  at  173°  to 
a  clear  oil  with  no  effervescence.  It  is  difficultly  soluble  in 
water  and  moderately  soluble  in  cold  acetone ;  insoluble  in  cold 
benzene  and  ether;  and  difficultly  soluble  in  chloroform.  It 
was  insoluble  in  cold  25  per  cent  hydrochloric  and  sulphuric 
acids  and  easily  soluble  in  warm  glacial  acetic  acid.  Analysis 
(Kjeldahl) : 

Calculated  for  Pound. 

CuHio02N2.  I.  H. 

N  13-86  13.9  14.0 

This  pyrimidine  does  not  react  with  diazobenzenesulphonic 
acid  to  give  a  red  colored  solution.     The  mixture  assumed  a 
yellow  color,  which  was  permanent  for  30  minutes. 
^Solubility  of  j-Benzyluracil  in  Water. — One  hundred  parts 
of  water  dissolved  at  25° 

i.  n. 

0.0998  gram.  0.1008  gram. 

NH CO 

I  I 

3-Benzyl-5-bromuracil,  CO        CBr. — This   pyrimi- 

I  II 

C6H5CH2.N CH 

dine  can  be  prepared  by  treating  3-benzyluracil  in  glacial  acetic 
acid  with  the  calculated  quantity  of  bromine.  It  crystallizes  from 
acetic  acid  in  hexagonal  prisms  melting  at  204°  to  a  clear  oil. 
The  same  brompyrimidine  was  also  prepared  by  dissolving 
0.5  gram  of  3-benzyluracil  in  bromine  water  and  allowing  the 
solution  to  evaporate  to  dryness.  The  residue,  about  0.8-0.9 
gram,  was  then  digested  with  absolute  alcohol  for  2  hours 
and  the  solution  evaporated  to  dryness.  The  compound 
obtained  by  this  treatment  crystallized  from  alcohol  in  prisms 
melting  at  204°.  A  quantitative  yield  of  the  pyrimidine  was 
also  obtained  by  digesting  2-ethylmercapto-3-benzyl-5-brom- 
6-oxypyrimidine  with  concentrated  hydrochloric  acid.  Anal- 
ysis (Kjeldahl) : 

Calculated  for  Found. 

CiiH9OaN2Br. 

N  9.96  10.0 


454  Johnson  and  Derby,  Jr. 

NH  -  CO 

I  I 

3-p-Nitrobenzyl-5-nitrouracil,  CO        CNO2.  — 

NO2.CCH4CH2.N  --  CH 

Five-tenths  of  a  gram  of  3-benzyluracil  was  dissolved,  at 
ordinary  temperature,  in  10  cc.  of  fuming  nitric  acid  of  density 
1.5.  The  acid  solution  was  then  allowed  to  stand  at  ordinary 
temperature  when  prismatic  crystals  separated.  They  were 
purified  for  analysis  by  recrystallization  from  hot  water.  The 
pyrimidine  is  difficultly  soluble  and  separates  in  slender  prisms, 
which  decompose,  according  to  the  rate  of  heating,  at  2^^-240° 
with  effervescence  .  Analysis  (Kjeldahl)  : 

Calculated  for  Found. 

CnH806N4.          CnH904N8.  I.  II. 

N  19.18  17.00  19-48  19-39 

CH3N  -  CO 

I  I 

i-M  ethyl-  3-benzyluracil,  CO        CH.  —  This  pyrimi- 

C8H5.CH2N  -  CH 

dine  is  easily  prepared  by  dissolving  3-benzyluracil  and  one 
molecular  proportion  of  potassium  hydroxide  in  alcohol  and 
then  warming  with  an  excess  of  methyl  iodide.  The  same 
pyrimidine  was  also  obtained  when  i-methyluracil1  was  digested 
in  alcohol  with  the  calculated  proportions  of  potassium  hy- 
droxide and  benzyl  chloride.  The  pyrimidine  is  extremely 
soluble  in  alcohol  and  benzene.  It  crystallizes  from  dilute 
alcohol  in  needles  melting  at  75  °  to  an  oil  without  effervescence. 
Analysis  (Kjeldahl): 

Calculated  for  Found. 


N  12.96 

i-M  ethyl-  3-benzyl-5-bromuracil, 

C8H5CH2N 
pyrimidine  was  prepared  in  two  ways: 

1  Johnson  and  Heyl:  Loc.  cit. 


Researches  on  Pyrimidines.  455 

1.  By  dissolving   i-methyl-3-benzyluracil  in  glacial  acetic 
acid   and   then   adding   the   calculated   amount   of   bromine. 
They  reacted  with  evolution  of  heat.     The  pyrimidine  was  very 
soluble  in  glacial  acetic  acid  but  was  precipitated  by  dilu- 
ting with  water. 

2.  By  warming  0.8  gram  of  3-benzyl-5-bromuracil  in  methyl 
alcohol  with  1.9  grams  of  methyl  iodide  and  o.i  gram  of  me- 
tallic sodium.     The  alkylation  was  very  smooth  and  the  solu- 
tion was  neutral  in  a  few  minutes.     The  pyrimidine  crystallizes 
from  alcohol  in  diamond-shaped  prisms  melting  at  123°  to  a 
clear  oil  with  no  effervescence.     Analysis  (Kjeldahl) : 

Calculated  for 

CiaHjiOjNaBr,  Found. 

N  9.50  9.8 

2-Ethylmercapto-i-benzyl-5-methyl-6-oxypyrimidine, 
C8H5CH2N CO 

C2H5SC  CCH3. — Fifteen  grams  of  2-ethylmercapto-5- 

II  II 

N CH 

methyl-6-oxypyrimidine  and  4.9  grams  of  finely  pulverized 
potassium  hydroxide  were  dissolved  in  75  cc.  of  absolute 
alcohol.  Eleven  and  two- tenths  grams  of  benzyl  chloride 
were  then  added  and  the  solution  heated  on  the  steam  bath 
for  6  hours.  After  filtering  from  undissolved  potassium 
chloride  and  evaporation  of  the  alcohol  we  obtained  a  crystal- 
line product  which  was  washed  with  50  cc.  of  a  5  per  cent 
solution  of  sodium  hydroxide.  Four  and  four-tenths  grams  of 
unaltered  pyrimidine  deposited  when  the  sodium  hydroxide 
solution  was  acidified  with  acetic  acid.  The  crystalline  ma- 
terial, insoluble  in  sodium  hydroxide,  was  then  extracted  in 
the  usual  manner  with  ether  and  the  insoluble  portion  saved 
(see  3 -benzyl  derivative  below).  From  the  ether  washings 
we  obtained  about  3.0  grams  of  pyrimidine  melting  at  65°-66°. 
The  compound  is  very  soluble  in  acetone,  benzene,  and  ether. 
It  separates  from  dilute  alcohol  in  stout  prisms  melting  at 
70°  to  a  clear  oil  without  effervescence.  Analysis  (Kjeldahl) : 

.'t  Calculated  for 

Ci4Hi6ON2S.  Found. 

N  10.77  Jo-9 


456  Johnson  and  Derby,  Jr. 

2-Ethylmercapto-3-benzyl-$-methyl-  6 -oxy pyrimidine, 
N CO 

H3. — The  crystalline  material,  which  was 

I  II 

C6H5CH2N CH 

insoluble  in  ether,  in  the  above  experiment  represented  this 
pyrimidine  and  weighed  11.2  grams,  corresponding  to  68  per 
cent  of  the  calculated.  The  pyrimidine  is  extremely  soluble 
in  alcohol  and  acetone.  It  was  purified  for  analysis  by  re- 
crystallization  from  benzene.  It  separated  in  hexagonal 
plates  melting  at  121°- 122°.  Analysis  '(Kjeldahl) : 

Calculated  for 
I.  Ci4H16ON2S.  Found. 

N                                10.77  ii. i 

C6H5CH2N CO 

i-Benzyltkymine,  CO         CCH3. One    and    eight- 

NH CH 

tenths  grams  of  i-benzyl-2-ethylmercapto-5-methyl-6-oxypyr- 
imidine  were  digested  with  concentrated  hydrochloric  acid  until 
the  evolution  of  ethyl  mercaptan  ceased.  When  this  solution  was 
evaporated  to  dryness  the  benzylthymine  was  obtained  as  a 
crystalline  compound.  The  pyrimidine  separated  from  hot 
alcohol  in  clusters  of  radiating  prisms  which  melted  at  204°- 
205°  to  a  clear  oil.  The  pyrimidine  is  difficultly  soluble  in 
water.  Analysis  (Kjeldahl) : 

Calculated  for 
CuHi2O2N2.  Found.    . 

N  12.96  13.3 

This  compound  reacted  with  diazobenzenesulphonic  acid,  in 
presence  of  sodium  hydroxide,  giving  a  beautiful,  claret  red 
solution. 

NH — CO 

I  I 

3-Benzylthymine,  CO         CCH3. — A  quantitative 

I  II 

C«H5CH2N CH 

yield  of  this  pyrimidine  was  obtained  when  the  corresponding 


Researches  on  Pyrimidines.  457 

2-mercaptopyrimidine  was  digested  with  concentrated  hy- 
drochloric acid  until  the  evolution  of  ethyl  mercaptan  ceased. 
The  pyrimidine  is  easily  soluble  in  alcohol,  acetone,  benzene, 
and  difficultly  soluble  in  ether.  It  is  very  soluble  in  glacial 
acetic  acid  and  chloroform  and  difficultly  soluble  in  cold  25 
per  cent  hydrochloric  and  sulphuric  acids.  It  separates  from 
hot  water  in  diamond-shaped  prisms  melting  at  160°  to  a  clear 
oil  with  no  effervescence.  Analysis  (Kjeldahl)  : 

Calculated  for 


Found. 

N  12.96  13.2 

This  pyrimidine  did  not  react  with  diazobenzenesulphonic 
acid  to  give  a  red  color.  The  mixture  assumed  a  yellow  color 
which  remained  permanent  for  over  one  hour. 

Solubility  of  3-Benzylthymine  in  Water.  —  One  hundred  parts 
of  water  dissolved  at  25  ° 

i. 
0.1172  gram. 


i-Methyl-j-benzylthymine,  CO        CCH3. — From  3- 

C6H5CH2N CH 

benzylthymine  and  methyl  iodide.  It  crystallized  from  water 
in  prismatic  crystals  melting  at  101°  to  a  clear  oil.  It  did  not 
react  with  diazobenzenesulphonic  acid  to  give  a  red  color. 
Analysis  (Kjeldahl) : 

Calculated  for 
C^HuOaNa.  Found. 

N  12.17  12.07 

3-p-Nitrobenzyloxynitrohydrothymine, 

NH CO 

I  I      CH3 

CO        C<        .—Five-tenths     of    a    gram    of 


|  I      NO, 


NO2CeH4CH2N CHOH 

3 -benzylthymine  was  dissolved  in  10  cc.  of  cold  fuming  nitric 
acid  of  density  1.5.     There  was  only  slight  evolution  of  heat 


458  Johnson  and  Derby ,  Jr. 

and  the  pyrimidine  dissolved  to  a  clear,  yellow  solution.  On 
standing  exposed  to  the  atmosphere  well-developed  prisms 
separated.  They  decomposed  at  176°  with  violent  efferves- 
cence. A  nitrogen  determination  indicated  that  a  nitro  group 
had  entered  the  benzene  ring  and  that  nitric  acid  had  added  to 
the  double  bond  in  the  4,5  positions  of  the  pyrimidine  ring. 
Analysis  (Kjeldahl) : 

Calculated  for 
Ci2Hl207N4.         Ci8H1305N3.        C12Hn04N3?         Found. 

N  17.28  14.33  16.0  17.11 

NBW  HAVBN,  CONN., 
June,  1908. 


-i 


[Reprinted  from  The  American  Chemical  Journal, 
Vol.  XI,.    No.  6.    December,  1908.] 


[Contributions  from  the  Sheffield  Laboratory  of  Yale  University.] 

CLXIIL— RESEARCHES  ON  PYRIMIDINES: 
SYNTHESES  OF  NEW  DERIVATIVES  OF  5-HYDROXY- 
URACIL (ISOBARBITURIC  ACID). 

(  [THIRTY-NINTH  PAPER.] 

BY  TREAT  B.  JOHNSON  AND  D.  BREESE  JONES. 

Johnson  andClapp1  have  shown  that  i-  and  3 -alky  1  derivatives 
of  2,6-dioxytetrahydropyrimidines,  I.,  can  be  distinguished 
by  the  difference  in  their  behavior  towards  diazobenzene- 
sulphonic  acid.  The  i-alkylpyrimidines,  II.,  react  with  the 
sulphonic  acid,  in  presence  of  alkali,  giving  red  colored  solutions, 
while  the  isomeric  3-alkylpyrimidines,  III.,  do  not  give  red 
colors  under  the  same  conditions.  This  interesting  behavior 
of  i-alkylpyrimidines  enabled  Johnson  and  Derby2  to  de- 
termine the  structures  of  the  isomeric  i-  and  3-benzyl  deriva- 
tives of  uracil  and  thymine. 

NH CO         Alk—N CO  NH CO 

II  II 

CO       C—  CO       C— 

I      II  I      II 

NH C—  Alk—N C— 

II.  III. 

We  have  also  found  this  diazo  reagent  to  be  of  service  for 
determining  the  structures  of  some  new  i-  and  3-alkyl  deriva- 
tives of  isobarbituric  acid.  The  name — isobarbituric — signifies 
a  compound  isomeric  with  barbituric  acid,  IV.,  and  having 
the  constitution  of  a  hexahydropyrimidine,  as  represented  by 
formula  V.  The  reactions  of  this  pyrimidine,  however,  do 
not  indicate  a  hexahydro  compound  but  rather  a  tetrahydro- 
pyrimidine,  as  represented  by  formula  VI.,  viz.,  5-hydroxyuracil. 

NH CO  NH CO  NH- 

II  II 

CO       CH2  CO       CO  CO       C.OH 

NH CO  NH CH2 

iv.  v. 

»  J.  Biol.  Chem.,  5,  163  (1908). 
»  THIS  JOURNAL,  40,  444  (1908). 


Researches  on  Pyrimidines. 


539 


Formula  VI.  is  supported  by  the  facts  that  the  pyrimidine 
does  not  give  an  oxime1  and  also  that  the  hydrogen  of  the 
5-hydroxyl  group  is  replaceable  by  the  acetyl  radical2  when 
the  pyrimidine  is  warmed  with  acetic  anhydride.  Further- 
more, the  pyrimidine  and  its  ethyl  ether3  react  with  diazo- 
benzenesulphonic  acid,  giving  red  colors  as  intense  as  that 
obtained  with  thymine.4 

We  shall  describe  in  this  paper  the  preparation  and  prop- 
erties of  i-benzyl-5-hydroxyuracil  (i-benzylisobarbituric  acid), 
VII.,  3-benzyl-5-hydroxyuracil  (3-benzylisobarbituric  acid), 
VIII.,  and  also  i-benzylisodialuric  acid,  IX. 


C6H5CH,N- 
CO 


-CO 

COH 


NH- 
CO 


NH — CH      C6H6CH2 

VII.  VIII. 


-CO 
COH 
-CH 


C6H5CH3N CO 

CO       COH 

I  II 

NH — COH 

IX. 


Johnson  and  McCollum5  have  shown  that  pseudoethylthio- 
urea  condenses  smoothly  with  the  sodium  salt  of  ethyl  a-ethoxy- 
/?-oxyacrylate,  giving  2-ethylmercapto-5-ethoxy-6-oxypyrimi- 
dine,  X.  This  mercaptopyrimidine  reacted  with  benzyl 
chloride,  in  presence  of  alkali,  giving  two  isomeric  pyrimidines, 
wz.,  i-benzyl-2-ethylmercapto-5-ethoxy-6-oxypyrimidine,  XII., 
melting  at  i4O°-i4i°,  and  2-ethylmercapto-3-benzyl-5-ethoxy- 
6-oxypyrimidine,  XIII.,  melting  at  85°-86°.  We  did  not 
observe  the  formation  of  2-ethylmercapto-5-ethoxy-6-benzoxy- 
pyrimidine,  XI.  These  two  mercaptobenzylpyrimidines,  XII. 
and  XIII.,  were  converted  smoothly  by  hydrolysis  with  hy- 
drochloric and  hydrobromic  acids  into  i-benzyl-5-hydroxy- 
uracil,  XVII.,  melting  at  230°,  and  3-benzyl-5-hyroxyuracil, 
XIX.,  melting  at  2OO°-2io°,  respectively.  We  also  succeeded 
in  isolating  the  two  intermediate  products  of  the  hydrolysis, 
viz.,  i-benzyl-5-ethoxyuracil,  XIV.,  melting  at  150°,  and 
3-benzyl-5-ethoxyuracil,  XVI.,  melting  at  i63°-i64°. 

1  Behrend  and  Roosen:  Ann.  Chem.  (Liebig),  251,  240. 

2  Behrend  and  Roosen:  Loc.  cit. 

3  Johnson  and  McCollum:  J.  Biol.  Chem.,  1,  437 ;  THIS  JOURNAL,  36,  154. 

4  Johnson  and  Clapp:  Loc.  cit. 
6  Loc.  cit. 


540 


Johnson  and  Jones. 


HfT 

5 

o    o 
o  —  o  = 

=S  j    8-8=g  .    8-1 
PI           6     1 

M 

ffl     o                  w      ^ 

N 

ffl            .    &                                                               e*                       " 

« 

3 

s                 ^ 

°*                     0 

°« 

ON 

a                 E 

0°                               0° 

d° 

>  I 

af 

0°    .            ffl 

HrT          ffl                                                    " 

a                 ffi 

a 

o    o    a      °    °- 
cf|~0=C|M'    1 

=S       8-8=S       8-2- 
1  > 

X                        1   M 

IP 

II         i«-g_0  = 

a    o    a            o 

-** 

55     co                       2> 

a 

nT                ffi 

o 

cT                     °M 

a 

y\  * 

v 

/  \ 

h-p 

a9 

sXg,   8-^,    8-§=S, 

X                       ffi 

K* 

w  ^ 

^  £j  _ 

t7  —  ^  £5  —  O  —  ^J        ^  ^;  —  o  - 

—  Jz; 

o     ^ 
cf 

rf              gw 

S-           & 

o"                     ^ 

Researches  on  Pyrimidines.  541 

The  structures  of  these  pyrimidines  were  established  in  the 
following  manner:  The  i-benzyl-5-hydroxyuracil,  XVII.,  melt- 
ing at  230°,  and  the  corresponding  ethyl  ether,  XIV.,  reacted 
with  diazobenzenesulphonic  acid  in  presence  of  sodium  hy- 
droxide, giving  beautiful  red  colors.  The  isomeric  benzyl  hy- 
droxyuracil,  XIX.,  melting  at  2OO°-2io°,  and  its  ethyl  ether, 
XVI.,  did  not  react  with  the  sulphonic  acid,  with  formation 
of  red  colors,  indicating  that  these  pyrimidines  are  3-benzyl 
derivatives,  as  represented  by  the  formulas  above. 

The  benzyl-5-hydroxyuracils  and  their  ethyl  ethers  are 
difficultly  soluble  in  water.  The  hydroxyuracils  are  weak 
acids  and  stable  in  the  presence  of  hydrochloric  acid  below 
100°.  i-Benzyl-5-hydroxyuracil,  XVII.,  was  converted  prac- 
tically quantitatively  into  5-hydroxyuracil  (isobarbituric  acid), 
XV.,  when  heated  with  concentrated  hydrochloric  acid  at 
I5o°-i6o°. 

i-Benzyl-5-hydroxyuracil,  XVII.,  was  converted  quantita- 
tively into  i  -benzylisodialuric  acid,  XVIII.,  when  it  was 
suspended  in  cold  water  and  then  dissolved  by  adding  a  molec- 
ular proportion  of  bromine.  The  isodialuric  acid  crystal- 
lized from  hot  water  without  decomposition  and  gave  a  violet 
colored  salt  with  barium  hydroxide. 

EXPERIMENTAL  PART. 

i-Benzyl-2-ethylmercapto-5-ethoxy-6-oxypyrimidine, 
C6H5CH2N  -  CO 

C          COC2H5.—  2-Ethylmercapto-5-ethoxy-6-oxy- 


N  --  CH 

pyrimidine1  (34  grams)  and  one  molecular  proportion  of 
potassium  hydroxide  (9.0  grams)  were  dissolved  in  250  cc.  of 
boiling,  absolute  alcohol.  Twenty-one  and  five-tenths  grams 
of  benzyl  chloride  were  then  added  and  the  solution  boiled 
until  it  gave  no  alkaline  reaction  when  tested  with  moist 
turmeric  (about  2  to  2.5  hours).  The  undissolved  potassium 
chloride  was  then  separated  by  filtration  and  the  excess  of 

1  Johnson  and  McCollum:  Loc.  cit. 


542  Johnson  and  Jones. 

alcohol  removed  by  evaporation  on  the  steam  bath.  We 
obtained  a  syrup  which  completely  solidified  after  trituration 
with  about  30  to  50  cc.  of  a  10  per  cent  solution  of  sodium 
hydroxide.  When  the  alkaline  solution  was  acidified  with 
acetic  acid  we  recovered  3.8  grams  of  the  unaltered  2-ethyl- 
mercaptopyrimidine.  The  crude  benzylpyrimidines  were  then 
extracted  3  times  with  boiling  ether  and  the  ether  solutions 
saved  (see  3-benzyl  derivative  below).  The  i-benzylpyrimi- 
dine  was  insoluble  in  ether  and  melted  without  further  purifi- 
cation at  i34°-i36°  to  an  oil.  It  was  purified  for  analysis 
by  recrystallization  from  acetone  or  hot  water.  It  separated 
in  slender  prisms  melting  at  140°— 141°  to  an  oil  without 
effervescence.  The  compound  is  very  soluble  in  alcohol, 
benzene,  and  acetone.  It  crystallizes  from  water  in  anhydrous 
condition.  Analysis  (Kjeldahl) : 

Calculated  for  Found. 

C15H18O2N2S.  I.  II. 

N  9.65  9.81  9.80 

2-Ethylmercapto-3-benzyl-5-ethoxy-6-oxypyrimidine, 
N CO 

II  I 

CaHgSC          COC,H6.— When  the  ether  washings  from   the 

C6H5CH2N CH 

above  experiment  were  heated  on  the  steam  bath  to  remove 
the  ether  we  obtained  a  syrup  which  partially  solidified  after 
standing  for  3  to  4  days.  The  crystalline  material  was  sepa- 
rated from  a  small  amount  of  oil  by  suction  filtration  and  re- 
crystallized  from  95  per  cent  alcohol.  It  deposited,  on  cooling, 
in  heavy,  prismatic  crystals  which  melted  at  85°-86°  to  a  clear 
oil  with  no  effervescence.  The  pyrimidine  is  very  soluble  in 
acetone,  alcohol,  and  ether,  but  insoluble  in  cold  water.  Anal- 
ysis (Kjeldahl): 

Calculated  for 
Cl6Hi8O2N8S.  Found. 

N  9 . 65  9 . 30 

The  total  yields,  and  relative  proportions  of  the  crude  iso- 
meric  benzylpyrimidines  obtained  in  4  experiments  by  alkyla- 


Researches  on  Pyrimidines.  543 

tion  of  the  mercaptopyrimidine,  are  given  in  the  following 
table: 


Its 

«j  ^ 

!1 

if 

wo  a 

P|O 

o-o  a 
fill 

o  <y  P<> 
•*•*£{  ^.2  2 

^rt 

Percentage  y 
of  i-  and  3-b 
derivatives. 

36.0 

24.7 

2.5 

93-4 

or 

or 

59-3% 

40-7% 

23-5 

17-5 

3-8 

94.0 

or 

or 

57-3% 

42.7% 

16.0 

4.0 

3-0 

92-5 

or 

or 

80.0% 

20.0% 

£-n  . 

c  >>a 

A  e-s 


•as«g 
'^  i$o 

47-5 


34-0 


18.0 


4         5-0  4-5 

C6H6CH2N CO 

i~Benzyl-5-ethoxyuracil,  CO       COC2H5. — Thispyrim- 

NH CH 

idine  was  always  obtained  mixed  with  i-benzyl-5-hydroxy- 
uracil  (see  below)  by  hydrolysis  of  i-benzyl-2-ethylmercapto- 
5-ethoxy-6-oxypyrimidine  with  concentrated  hydrochloric  acid. 
In  one  experiment,  5  grams  of  the  mercaptopyrimidine  were 
dissolved  in  150  cc.  of  concentrated  hydrochloric  acid  and  the 
solution  boiled  for  12  hours.  When  the  hydrochloric  acid  was 
removed,  by  heating  on  the  steam  bath,  we  obtained  a  mixture 
of  the  ethoxypyrimidine  and  benzylhydroxyuracil  melting  at 
i4O°-i8o°.  They  were  separated  from  each  other  by  frac- 
tional crystallization  from  95  per  cent  alcohol.  This  pyrim- 
idine  was  more  soluble  in  alcohol  than  the  hydroxyuracil 
and  crystallized  in  characteristic  hexagonal  prisms  melting  at 
150°  to  an  oil.  This  melting  point  was  not  raised  by  recrystal- 
lization  from  water.  The  pyrimidine  did  not  contain  water 
of  crystallization  and, did  not  give  a  test  for  sulphur.  When 


544  Johnson  and  Jones. 

it  was  dissolved  in  bromine  water,  and  barium  hydroxide  added 
to  the  solution,  a  purple  precipitate  was  obtained. 

The  pyrimidine  reacted  with  diazobenzenesulphonic  acid, 
in  presence  of  sodium  hydroxide,  giving  a  brilliant,  red  colored1 
solution.  The  color  slowly  faded  on  standing.  Analysis: 

0.1160  gram  of  substance  gave  n.8  cc.  N  at  19°  and  759  mm. 

Calculated  for 
C13H14O3N2.  Found. 

N  11.38  ii. 6 

i-Benzyl-5-hydroxyuracil  (i-Benzylisobarbituric  Acid), 
C6H5CH2.N CO 

O       C.OH. — 2-Bthylmercapto-i-benzyl-5-ethoxy-6- 

I  II 

NH CH 

oxypyrirnidine  is  not  converted  quantitatively  into  this  pyrimi- 
dine by  boiling  with  hydrochloric  acid.  In  order  to  obtain  a 
complete  hydrolysis  within  a  few  hours  we  found  it  necessary 
to  proceed  under  the  following  conditions:  36  grams  of  the 
mercaptopyrimidine  were  dissolved  in  about  500  cc.  of  con- 
centrated hydrochloric  acid  and  the  solution  evaporated  to 
dryness.  We  obtained  a  crystalline  mixture  of  the  interme- 
diate ethoxypyrimidine  (see  above)  and  the  benzylhydroxyura- 
cil,  which  was  then  dissolved  in  40  to  50  cc.  of  hydrobromic  acid. 
After  3  to  4  hours'  digestion  with  this  acid  the  hydrolysis  was 
complete.  Too  long  digestion  with  hydrobromic  acid  is  not 
advisable  because  the  benzylhydroxyuracil  slowly  undergoes 
decomposition  with  formation  of  benzyl  bromide  and  5-hy- 
droxyuracil.  After  removal  of  the  hydrobromic  acid  the  pyrim- 
idine was  purified  by  several  recrystallizations  from  alcohol  and 
water.  The  yield  was  good.  The  pyrimidine  is  less  soluble 
in  alcohol  than  the  corresponding  ethoxy  derivative  (see  above) . 
It  crystallizes  from  alcohol  in  clusters  of  radiating  prisms 
melting  at  230°  to  an  oil  with  effervescence.  The  pyrimidine 
separates  from  hot  water  in  corpuscular  crystals  resembling  in 
appearance  the  crystalline  form  of  5-hydroxyuracil  (Analysis 
III.).  A  violet  purple  precipitate  was  obtained  when  the 

1  Johnson  and  Clapp:  LOG.  cil. 


Researches  on  Pyrimidines.  545 

pyrimidine  was  dissolved  in  bromine  water  and  barium  hy- 
droxide added  to  the  solution.  The  pyrimidine  reacts  with 
diazobenzenesulphonic  acid,  in  presence  of  sodium  hydroxide, 
giving  as  intense  a  red  color  as  i-benzyl-5-ethoxyuracil.  Anal- 
yses: 

I.  0.0925  gram  substance  gave  10.2  cc.  N  at  19°  and  756 
mm. 

II.  and  III.  Nitrogen  by  Kjeldahl  method. 

Calculated  for  Found. 

CuHl003N2.  I.  II.  III. 

N  12.84  12. 60  12.95  ^Z-° 

5-Hydroxyuracil  (Isobarbituric  Acid)  from  i -Benzyl- 2-ethyl- 
mercapto-5~ethoxy-6-oxy  pyrimidine. — About  3.5  grams  of  the 
mercaptopyrimidine  were  dissolved  in  50  cc.  of  concentrated 
hydrochloric  acid  and  the  solution  heated  for  3  hours  at  150°- 
160°.  When  the  tube  was  opened  there  was  no  pressure,  and 
oil  floated  on  the  surface  of  the  solution.  This  was  separated 
and  identified  as  a  mixture  of  ethyl  mercaptan  and  benzyl- 
chloride.  When  the  acid  solution  was  evaporated  to  dryness, 
we  obtained  a  colorless  substance  which  was  difficultly  soluble 
in  water.  It  crystallized  from  hot  water  in  hard,  corpuscular 
crystals,  which  decomposed  without  melting  at  about  300°. 
It  did  not  contain  sulphur  and  chlorine.  When  the  compound 
was  dissolved  in  bromine  water  and  barium  hydroxide  added 
to  the  solution,  a  purple  precipitate  was  obtained.  A  nitrogen 
determination  agreed  with  the  calculated  value  for  5-hydroxy- 
uracil.1 

0.1321  gram  substance  gave  25.4  cc.  N  at  22°  and  750  mm. 

Calculated  for 

C4H4O3N2.  Found. 

N  21.87  21.48 

NH CO 

I  I 

S-Benzyl-j-ethoxyuracil,  CO       COC^H,.. — This  pyrim- 

C8H5CH2.N CH 

idine  was  formed  smoothly  when  2-ethylmercapto- 
3-benzyl-5-ethoxy-6-oxypyrimidine  was  digested  with  con- 

1  Behrend  and  Roosen:  Loc.  cit. 


546  Johnson  and  Jones. 

centrated  hydrochloric  acid.  It  appeared  to  be  more  stable, 
in  presence  of  hydrochloric  acid,  than  the  isomeric  i-benzyl- 
pyrimidine.  The  compound  is  difficultly  soluble  in  cold  water 
but  separates  from  a  hot  solution  in  needlelike  prisms.  It  is 
very  soluble  in  alcohol  and  separates  from  this  solvent  in  the 
form  of  plates.  It  melts  at  i63°-i64°  to  a  clear  oil.  When 
the  pyrimidine  is  dissolved  in  bromine  water  and  barium 
hydroxide  is  added  to  the  solution  a  violet  precipitate  is  ob- 
tained. The  pyrimidine  did  not  react  with  diazobenzene- 
sulphonic  acid  to  give  a  red  colored  solution.  The  solution  as- 
sumed a  yellow  color  which  was  permanent  for  20  minutes. 
Analysis  (Kjeldahl): 

Calculated  for  Found. 

C13H1408N2.  I.  II. 

N  11.38  11.23  11.40 

3-Benzyl-5-hydroxyuracil     (j-Benzylisobarbituric    Acid), 
NH CO 

CO       COH. — This   compound   was   obtained   when 

C6HBCH2.N CH 

2-ethylmercapto-3-benzyl-5-ethoxy-6-oxypyrimidine  was  di- 
gested for  several  hours  with  hydrobromic  acid.  The  pyrimi- 
dine crystallized  from  acetic  acid  in  irregular  crystals  which 
melted  from  200°  to  210°  according  to  the  rate  of  heating. 
It  was  difficultly  soluble  in  water  and  alcohol. 
Analysis  (Kjeldahl) : 

Calculated  for 
CuHl0O3N2.  Found. 

N                                 12.84  12.63 

C6H5CH2N CO 

I'Benzylisodialuric    Acid,  CO       COH. — Five    and 

I  II 

NH COH 

eight-tenths  grams  of  finely  pulverized  i-benzyl-5-hydroxyur- 
acil  were  suspended  in  50  cc.  of  ice  water,  and  4.5  grams  of 
bromine  slowly  added  to  the  solution  with  constant  stirring. 
The  bromine  immediately  disappeared  and  the  pyrimidine 


Researches  on  Pyrimidines.  547 

completely  dissolved.  The  excess  of  water  was  then  removed 
by  distillation  under  diminished  pressure  at  a  temperature  of 
50°  to  70°.  The  isodialuric  acid  finally  separated  from  the 
warm,  saturated  solution  in  beautiful,  prismatic  crystals. 
The  solution  was  then  cooled  and  the  crystals  separated  by 
filtration.  The  yield  of  crude  material  was  6.1  grams.  The 
pyrimidine  is  very  soluble  in  hot  water  and  separates,  on  cool- 
ing, in  lenticular  crystals  melting  at  139°  with  effervescence. 
The  pyrimidine  dissolved  in  a  solution  of  barium  hydroxide 
with  formation  of  a  violet  colored  solution.  When  heated  at 
105°  the  pyrimidine  slowly  underwent  decomposition. 

Analysis  : 

0.0979  gram  substance  gave  10  cc.  of  N.at  20°  and  768  mm. 

Calculated  for 

.  Found. 


N  11.96  n.  Si 


NEW  HAVEN,  CONN., 
June.  1908. 


[Reprinted  from  the  American  Chemical  Journal,  Vol,  XL. 
No.  6.    December,  1908.] 


[Contributions  from  the  Sheffield  Laboratory  of  Yale  University.] 

CLXIV.— RESEARCHES  ON  PYRIMIDINES: 
THE  THIO  DERIVATIVES  OF  URACIL  AND  THE  PREP- 
ARATION OF  URACIL  IN  QUANTITY. 

[FORTIETH  PAPER.] 
BY  HENRY  L.  WHEELER  AND  LEONARD  M.  LIDDLE. 

The  impression  is  given  in  several  text-books  that  the  prep- 
aration of  uracil,  thymine,  and  cytosine  by  our  synthetic 
methods1  is  no  easier  than  the  isolation  of  these  substances 
from  nucleic  acids.  Our  syntheses  are  even  given  in  Beil- 
stein2  as  a  process  of  formation  (Bildung)  and  not  as  the  best 
method  of  preparation  (Darstellung) .  This  view  of  our  work 
is  far  from  correct.  In  the  past  few  years  we  have  prepared 
a  number  of  kilograms  of  these  pyrimidines  by  our  methods. 
The  preparation  of  this  amount  of  these  substances  from  the 
nucleic  acids  would  be  a  task  for  a  factory. 

1  Wheeler,  Merriam,  and  Johnson:  THIS  JOURNAL,  29,  478  and  492  (1903). 

2  Erganzungsbande,  IV.,  550,  551,  1162. 


548  Wheeler  and  Liddle. 

For  the  preparation  of  uracil  the  sodium  salt  of  formyl- 
acetic  ester,  NaOCH=CHCO2C2H5,1  was  condensed,  in 
alkaline,  aqueous  solution,  with  a  pseudothiourea,  H2N — C 
(SC2H5)NH.  The  condensation  product,  2-ethylmercapto-6- 
oxypyrimidine,  on  boiling  with  hydrochloric  acid,  easily  gave 
off  mercaptan,  and  a  quantitative  yield  of  uracil  was  obtained. 

In  this  paper  we  describe  a  method  of  preparing  uracil  that 
is  an  improvement  even  over  our  previous  synthesis.  It  has 
been  our  experience  that  thiourea  gives  uniformly  larger  yields 
of  pyrimidine  derivative  than  ethylpseudothiourea2  when 
condensed  with  the  sodium  salt  of  formyl  acetic  ester. 

The  condensation  with  thiourea  takes  place  with  the  forma- 
tion of  2-thiouracil,  I.,8  as  follows: 

HNH  C2H5OCO  HN CO  C2H5OH 

SC       +  CH     =     SC         CH     + 

I  II  I         I! 

HNH  NaOCH  HN CH  NaQp 

This  condensation  has  the  advantage  over  our  previous 
method  of  avoiding  the  presence  of  mercaptan  and  since 
2-thiouracil  is  more  than  ten  times  less  soluble  than  2-ethyl- 
mercapto-6-oxypyrimidine  it  separates  more  nearly  com- 
pletely on  acidifying. 

It  remained  then  to  discover  a  simple  method  of  replacing 
the  sulphur  in  this  substance  by  oxygen.  2-Thiouracil,  like 
other  compounds  of  this  class,  is  not  desulphurized  readily, 
if  at  all,  by  the  ordinary  methods.  It  forms  more  or  less 
stable  salts  with  the  metallic  oxides.  List  had  a  similar  ex- 

1  Wislicenus:  Ber.  d.  chem.  Ges.,  20,  2931  (1887). 

2  We  have  repeated  our  earlier  attempts  to  condense  the   sodium    salt    of   ethyl 
formylacetate  with  urea  in  aqueous  solution,  and  thus  obtain  uracil  directly,  but  with- 
out success.     We  have  found  that  pyrimidine  condensations  which  fail  when  water 
is  used  as  the  solvent  may  be  brought  about  in  alcoholic  solution,  in    the    presence 
of  sodium  ethylate.     When  the  sodium  salt  of  ethyl  formylacetate,  urea,  and  sodium 
ethylate  were  warmed  for  an  hour  on  the  steam  bath  and  then  tested  for  uracil  with 
bromine  water  and  barium  hydroxide  (J.  Biol.  Chem.,  3,   183   (1907))  no  color  was 
obtained.     No    precipitate    was    formed    on    acidifying    the    concentrated    solution 
and  no  evidence  of  the  formation  of  uracil  was  observed. 

3  Wheeler  and  Bristol:  THIS  JOURNAL,  33,  458  (1905). 


Researches  on  Pyrimidines.  549 

perience  with  2-thio-4-methyluracil.1  To  desulphurize  this 
substance  it  was  necessary  to  heat  in  a  closed  tube  with  hydro- 
chloric acid  for  a  few  hours  at  I5o°-i6o°.  The  thiohydan- 
toins  evidently  also  belong  to  this  class.2 

After  a  number  of  experiments  we  found  that  when  2-thio- 
uracil  was  simply  boiled  with  an  aqueous  solution  of  chlor- 
acetic acid,  in  slight  excess,  sulphur  was  easily  removed,  and 
on  evaporation  uracil  remained.  The  yield  was  practically 
quantitative.  The  reaction  probably  involves  the  inter- 
mediate formation  of  the  unstable  6-oxypyrimidine-2-thio- 
gly collie  acid,  II.,  which,  as  we  show  below,  on  boiling  with 
water  gives  uracil,  III.,  and  thioglycollic  acid  or  its  decom- 
position products,  as  follows: 

HN CO  HN CO 

II  II 

HOCOCH2SC         CH  4-  H2O  =  OC        CH  +  HOCOCH2SH. 

II          0  I  II 

N CH  HN CH 

;-^-  II.  III. 

This  reaction,  which  introduces  nothing  which  can  not  be 
easily  removed,  is  so  smooth  and  satisfactory  that  we  intend 
to  investigate  the  use  of  chloracetic  acid  for  desulphurization 
in  other  cases.  At  present,  we  have  examined  simply  the  new 
thio  derivatives  of  uracil  in  this  respect  and  have  made  the 
curious  observation  that  while  2-thiouracil  and  6-thiouracil, 
VII.,  are  readily  desulphurized,  2 ,6-dithiouracil,  VIII.,  is  not 
desulphurized  on  boiling  with  chloracetic  acid  but  apparently 
forms  the  stable  pyrimidine,  2, 6-dithiogly collie  acid,  IX. 

The  preparation  of  the  new  thio  derivatives  of  uracil  was 
carried  ,  out  as  follows:  2-Ethylmercapto-6-chlorpyrimidine, 
V.,  from  2-ethylmercapto-6-oxypyrimidine,3  IV.,  was  treated 
with  potassium  hydrosulphide,  giving  2-ethylmercapto-6- 
thiopyrimidine,  VI. 

When  this  compound  was  treated  with  concentrated  hydro- 
chloric acid  on  the  steam  bath  mercaptan  was  evolved  and 

1  Ann.  Chem.  (Liebig),  236,  1  (1886). 

2  Bailey  and  Randolph:  Ber.  d.  chem.  Ges.,  41,  2495  (1908). 

3  Wheeler  and  Johnson:  THIS  JOURNAL,  29,  496  (1903). 


550  Wheeler  and  Liddle. 

6-thiouracil,  VII.,  was  formed.  On  heating  with  dry  hydro- 
gen chloride,  ethyl  chloride  was  given  off  and  2,6-dithiouracil, 
VIII.,  was  obtained.  The  latter  was  also  prepared  from 
2,6-dichlorpyrimidine,  X.,  and  potassium  hydrosulphide. 

HN CO  N=CC1  HN — CS 

II  II  II 

C2H6SC      CH    ->    C^SC       CH    ->•    C2H6SC       CH 

II        II  II         II  II        II 

N CH  N CH  N CH 

IV.  V.  VI. 

/       j 

N=CSCH2CO2H     HN CS  HN CS 

II  II  II 

HCO2CH2SC      CH        <-       SC       CH  OC       CH 

II        II  I        II  I        II 

N CH  HN CH  HN CH 

IX.  VIII.  VII. 

t 

N=CC1 

C1C       CH 

II        II 

N CH 

x. 

EXPERIMENTAL  PART. 
HN — CO 

2-ThiouracU,   SC      CH. — The  sodium  salt  of  formylacetic 

HN CH 

ester,  prepared  according  to  Wislicenus'1  directions  from  150 
grams  of  ethyl  formate,  150  grams  of  ethyl  acetate,  and  42 
grams  of  sodium  clippings  in  500-600  cc.  of  dry  ether,  was 
dissolved  in  a  cold,  saturated,  aqueous  solution  of  70  grams  of 
thiourea.  The  solution  was  allowed  to  stand  for  an  hour  or 
so,  then  warmed  on  the  steam  bath,  and  finally  cooled  and 
acidified  with  acetic  acid.  Four  such  experiments  gave  about 
280  grams  of  2-thiouracil. 

1  Ber.  d.  chem.  Ges..  20,  2933  (1887). 


Researches  on  Pyrimidines.  551 

A  portion  of  this  material  was  crystallized  from  water  until  it 
was  obtained  in  colorless  bunches  of  prismatic  plates  which 
melted  with  decomposition  at  about  340°.  A  solubility  deter- 
mination was  then  made  as  follows :  The  substance  was  placed 
in  cold  water  and  a  rapid  stream  of  air  was  drawn  by  suction, 
first  through  a  wash  bottle  containing  distilled  water,  and  then 
through  the  solution  containing  the  suspended  substance. 
After  two  hours  the  undissolved  material  was  filtered  off  and  a 
weighed  portion  of  the  solution  was  evaporated  to  dryness  and 
the  residue  was  heated  to  constant  weight  at  110°. 

To  check  the  results  a  parallel  series  of  determinations  were 
made  in  which  the  substance  was  dissolved  in  hot  water  and 
the  saturated  solution  was  allowed  to  cool  while  air  was  drawn 
through  for  two  hours  as  before.  Solubility  determinations 
were  also  made  in  this  manner  in  the  case  of  2-ethylmercapto- 
6-oxypyrimidine  and  2-methylmercapto-6-oxypyrimidine.  It 
was  found  that  100  parts  of  water  at  17°  dissolved: 

Hot  saturated       Cold  saturated 
solution.  solution. 

2-Thiouracil  0.0533  gram  0.0598  gram 

2-Methylmercapto-6-oxypyrimidine    0.6170      "      0.6620      " 
2-Ethylmercapto-6-oxypyrimidine       0.8000      "      0.7930      " 

The  mercaptopyrimidines  are  therefore  more  than  ten 
times  as  soluble  in  water  as  2-thiouracil.  2-Thiouracil  is  al- 
most insoluble  in  alcohol  while  the  mercapto  derivatives  are 
very  soluble.  In  our  pyrimidine  condensations  alcohol  is  al- 
ways present  as  a  by-product,  unless  removed  by  evaporation; 
this  reduces  the  yield  in  the  case  of  the  mercapto  derivatives 
while  in  the  case  of  thio  derivatives  just  the  opposite  is  true. 

In  accordance  with  its  thioamide  character,  2-thiouracil  is  a 
much  stronger  acid  than  uracil.  It  readily  dissolves  in  sodium 
or  potassium  hydroxides  and  it  forms  very  soluble,  crystalline, 
anhydrous  salts  with  these  bases.  It  can  be  very  conveniently 
crystallized  from  aqueous  ammonia  in  which  it  is  far  more 
soluble  than  in  water.  It  forms  an  ammonium  salt  which 
loses  ammonia  on  drying  or  on  boiling  with  water.  Mercuric 
oxide  removes  2-thiouracil  from  solution,  forming  an  amor- 
phous, anhydrous,  insoluble  salt. 


552  Wheeler  and  Liddle. 

The  Copper  Salt,  C4H2ON2SCu.H2O.— Copper  sulphate  pro- 
duces in  aqueous  solutions  of  2-thiouracil,  with  or  without 
alkali,  an  amorphous,  mustard- yellow,  insoluble  precipitate. 
This  salt  can  be  boiled  with  water  without  alteration.  It  was 
dried  in  a  desiccator  over  calcium  chloride  for  analysis. 

0.2997  gram  substance  lost  0.0276  gram  on  heating  two 
hours  at  io5°-ii5°. 

Calculated  for 
C4H2ON2SCu.H2O.  Found. 

H2O  8 . 67  9 . 20 

0.1167  gram  substance  gave  0.045  gram  CuO. 

Calculated  for 
C^HsONzSCu.HaO.  Found. 

Cu  30.60  30.76 

When  silver  nitrate  is  added  to  an  aqueous  solution  of 
2-thiouracil  an  amorphous,  gelatinous,  white  precipitate  is 
formed  which  does  not  blacken  on  boiling. 

HN CO 

Preparation  of  Uracil,  OC       CH. — Twenty  grams  of  2-thio- 

HN CH 

uracil  were  boiled  with  one  and  a  half  molecular  proportions  of 
chloracetic  acid  in  a  large  amount  of  water  for  one  hour,  then 
evaporated  to  dry  ness  on  the  steam  bath.  The  slightly 
colored  residue  was  decolorized  by  means  of  animal  charcoal, 
and  on  concentrating  the  solution  14.2  grams  of  pure  white 
uracil,  free  from  sulphur,  were  obtained.  The  yield  in  this 
case  was  81  per  cent  of  the  calculated.  More  could  have  been 
obtained  from  the  mother  liquor. 

In  another  experiment  30  grams  of  2-thiouracil  were  boiled 
with  33  grams  of  chloracetic  acid  in  about  700  cc.  of  water. 
When  the  material  had  dissolved  the  solution  was  allowed  to 
evaporate  to  dry  ness  on  the  steam  bath.  The  residue  was 
warmed  with  alcohol,  filtered,  and  washed  with  alcohol.  It 
was  then  free  from  sulphur  and  weighed  23.5  grams.  This  is 
89.5  per  cent  of  the  calculated. 

Uracil  from  6-Thiouracil. — An  aqueous  solution  of  2.1  grams 
of  6-thiouracil  was  mixed  with  3  grams  of  chloracetic  acid  and 


Researches  on  Pyrimidines.  553 

the  solution  was  then  evaporated  to  dryness  on  the  steam  bath. 
When  the  residue  was  crystallized  from  water  1.2  grams  of 
pure  uracil  separated.     This  is  66  per  cent  of  the  calculated. 
Ethyl  6-Oxypyrimidine-2-thioglycollate} 
HN CO 

I  I 

C2H5CO2CH2SC      CH.|H2O.— Five  grams  of  2-thiouracil  were 

II  II 
N CH 

mixed  with  a  solution  of  0.9  gram  of  sodium  in  30  cc.  of  alcohol 
and  then  4.8  grams  of  ethyl  chloracetate  were  added.  The 
mixture  was  heated  on  the  steam  bath  under  a  return  con- 
denser for  one  hour.  The  solution  was  then  filtered  and 
allowed  to  evaporate  under  reduced  pressure  in  a  desiccator. 
The  crystalline  residue  after  three  recrystallizations  from  water 
yielded  long,  thin,  glistening  plates.  These  gave  a  strong  test 
for  sulphur  and  melted  to  a  clear  oil  at  i54°-i55°.  The  sub- 
stance was  easily  soluble  in  hot  water  and  hot  alcohol  and 
nearly  insoluble  in  cold  water. 

0.2852   gram  substance  lost  0.0138  gram  when  heated  at 
ioo°-ii5°  for  two  hours. 

Calculated  for  Found. 

C8Hio03N2S.iH20.  I.  II.  III. 

H20     4.03      ....      ....     4.83 

N      12.55     12.44     12.57 

6-Oxypyrimidine-2-thioglycollic  Acid, 
HN CO 

I  I 

HOCOCH2SC       CH.H2O.— This  acid  was  obtained  from    the 

II  II 
N CH 

above  ester  by  warming  its  aqueous  solution  with  an  excess  of 
potassium  hydroxide  for  a  few  minutes  on  the  steam  bath. 
The  solution  was  then  cooled  and  acidified  with  hydrochloric 
acid.  A  heavy,  white  precipitate  formed  which  crystallized 
from  water  in  bunches  of  fine  prisms.  This  proved  to  be  the 
hydrous  form  which  separates  slowly  and  melts  at  178°.  If 
the  solution  is  stirred  or  the  beaker  scratched  the  anhydrous 
form  generally  results.  The  latter  separates  rapidly  in  loose 


554  Wheeler  and  Liddle. 

bunches  of  fine  needles.  The  substance  can  be  crystallized 
from  alcohol.  When  it  is  boiled  with  water,  thioglycollic 
acid  separates  and  uracil  is  obtained. 

0.2676  gram  substance  lost  0.0238  gram  when  heated  two 
hours  at  io5°-no°. 

Calculated  for  Found. 

C6H603N2S.H20.  I.  II.  III. 

H2O  8 . 82  8 . 89  .... 

N  13.72  13.90  13.65 

Some  experiments  were  made  with  the  object  of  preparing 
alkyl  derivatives  of  2-thiouracil.  If  a  smooth  alkylation  on 
the  sulphur  would  take  place  it  would  be  the  best  method  for 
the  preparation  of  2-alkylmercaptopyrimidines. 

2-Ethylmercapto-6-oxypyrimidine.1 — The  action  of  sodium 
,ethylate  and  ethyl  iodide  on  2-thiouracil  in  alcoholic  solution 
gave  2-ethylmercapto-6-oxypyrimidine,  melting  at  152  °.  When 
30  grams  or  more  of  2-thiouracil  were  employed  the  yields 
were  much  below  the  calculated.  Unaltered  2-thiouracil 
was  recovered  when  the  substances  were  allowed  to  act  in 
molecular  proportions.  It  required  repeated  recrystalliza- 
tions  from  alcohol  to  remove  this  impurity,  so  that  the  yields 
were  unsatisfactory.  If  an  excess  of  iodide  and  alkali  were 
used  the  yield  of  2-ethylmercapto-6-oxypyrimidine  was  still 
further  reduced,  owing  to  the  formation  of  higher  alkylated 
products.  It  was  found  that  benzyl  chloride  acted  more 
smoothly. 

HN CO 

2-Benzylmercapto-6-oxypyrimidine,   C6H5CH2SC       CH. — Ten 

N CH 

grams  of  2-thiouracil  and  4.4  grams  of  potassium  hydroxide 
were  dissolved  in  the  smallest  possible  quantity  of  water  on 
the  steam  bath  and  mixed  with  9.9  grams  of  benzyl  chloride. 
Alcohol  was  then  added  until  the  oil  went  into  solution.  The 
reaction  took  place  immediately  and  gave  long,  slender,  color- 
less prisms  weighing  11.7  grams,  or  68  per  cent  of  the  calculated. 

1  Wheeler  and  Merriam:  THIS  JOURNAL,  29,  478  (1903). 


Researches  on  Pyrimidines.  555 

The  same  quantities  of  substances  shaken  repeatedly  in  a 
separatory  funnel  in  aqueous  solution  without  alcohol  gave 
12.4  grams,  or  72  per  cent  of  the  calculated.  The  first  method 
of  preparation  is  smoother  and  is  much  easier,  the  product 
being  more  nearly  pure. 

The  substance  is  soluble  in  about  16  parts  of  hot  alcohol 
and  in  50  parts  of  cold.  In  water  or  ether  it  is  practically 
insoluble.  Recrystallization  from  alcohol  gave  slender,  twinned 
prisms  which  melted  to  a  clear  oil  at  i92°-i93°. 

Calculated  for 
CnHl0ON2S.  Found. 

N  12.88  12.88 

When  the  substance  was  warmed  with  hydrochloric  acid  on 
the  steam  bath,  benzyl  mercaptan  separated.  On  evaporating 
and  extracting  with  alcohol,  uracil  was  obtained. 

The  Sodium  Salt  of  2-Benzylmercapto-6-oxypyrimidinet 
C11H9ON2SNa.3H2O. — Themercapto  derivative  was  dissolved  in 
an  aqueous  solution  of  sodium  hydroxide  and  allowed  to  crystal- 
lize slowly  in  a  desiccator.  Large  talclike  plates  formed  which 
were  very  soluble  in  water  and  fairly  soluble  in  alcohol. 

0.3069  gram  of  substance  lost  0.056  gram  when  heated  at 
ioo°-iio°  for  two  hours. 

Calculated  for  Found. 

CuH9ON2SNa.3H20.  I.  II.  III. 

H2O          18.35  18.24  ....  

N  9.52  9.69  9.43 

HN CS 

I     I 

2-Ethylmercapto-6-thiopyrimidine,    C2H5SC       CH.  —Eight 

N CH 

grams  of  2-ethylmercapto-6-chlorpyrimidine1  were  treated  with 
two  and  a  half  times  the  calculated  quantity  of  potassium 
hydrosulphide  in  alcoholic  solution.  The  solution  was  boiled 
for  about  15  minutes  and  then  evaporated  to  dryness  on  the 
steam  bath  and  the  residue  taken  up  in  a  small  quantity  of 

*  Wheeler  and  Johnson:  THIS  JOURNAL,  29,  496  (1903);  31,  596  (1904). 


556  Wheeler  and  Liddle. 

water.  The  solution  was  shaken  with  ether,  to  remove  any 
6-ethoxy  or  unaltered  chlor  compound,  and  then  made  dis- 
tinctly acid  in  the  cold  with  acetic  acid.  A  white  flocculent 
precipitate  separated,  weighing  6.4  grams,  or  80  per  cent  of 
the  calculated.  The  substance  was  recrystallized  twice  from 
water,  when  it  gave  brilliant  needlelike  prisms,  having  a  pale 
yellow  color,  which  melted  to  a  yellow  oil  at  149°.  The  mate- 
rial was  easily  soluble  in  alcohol  and  moderately  in  hot  water. 
In  cold  water  it  was  nearly  insoluble.  The  properties  of  the 
compound  were  very  similar  to  those  of  2-ethylmercapto-6- 
oxypyrimidine,  but  a  mixture  of  these  substances  melted  at 
about  126°. 

Calculated  for 

CeH8N2S2.  Found. 

N  16.27  16.05 

HN  -  CS 

I     I 

6-Thwuracil,  OC       CH.  —  Two  grams  of  2-ethylmercapto-6- 

I         II 
HN  -  CH 

thiopyrimidine  were  evaporated  to  dryness  on  the  steam  bath 
with  10  cc.  of  concentrated  hydrochloric  acid.  Mercaptan 
escaped.  The  residue  was  extracted  with  cold  alcohol  to  re- 
move unaltered  ethylmercaptothiopyrimidine  and  the  in- 
soluble material  was  then  found  to  weigh  0.8  gram,  or  55  per 
cent  of  the  calculated.  In  another  experiment  more  prolonged 
action  of  acid  gave  a  yield  of  90.0  per  cent;  a  small  amount 
of  uracil  was  also  formed. 

Like  uracil  and  2-thiouracil,  6-thiouracil  is  practically  in- 
soluble in  strong  alcohol  but  moderately  soluble  in  hot  water. 
It  crystallized  from  hot  water  in  small,  light  yellow  needles. 
On  rapidly  heating  it  blackened  above  270°  and  melted  with 
effervescence  at  328°.  The  properties  of  this  substance  are 
closely  similar  to  those  of  2,6-dithiouracil  but  a  mixture  of 
these  compounds  melted  at  295°. 

Calculated  for 

Found. 


N  21.87  21.66 


Researches  on  Pyrimidines.  557 

HN  -  CS 

I         I 
2,6-Dithiouracil,  SC       CH.  —  A  portion  of  2  ,6-dichlorpyrimi- 

HN  -  CH 

dine1  was  warmed  on  the  steam  bath  with  an  aqueous  solu- 
tion containing  somewhat  more  than  four  times  the  calculated 
quantity  of  potassium  hydrosulphide.  As  soon  as  the  oil 
disappeared,  the  hot  solution  was  filtered  from  slight  im- 
purities and  acidified  with  hydrochloric  acid.  This  gave  a 
yellow  flocculent  precipitate  which  was  recrystallized  from 
water.  It  was  found  to  be  difficultly  soluble  and  it  gave  a 
feltlike  mass  of  fine,  bright  yellow  needles,  which  turned  dark 
and  decomposed  above  230°  without  showing  a  definite  melt 
ing  point. 

0.3215  gram  substance  gave  1.0278  gram  BaSO4. 

Calculated  for  Found. 

I.  II. 


S  44-44  43-79  ---- 

N  19-44  •  •  •  •  I9-46 

2,6-Dithiouracil  was  also  obtained  when  2-ethylmercapto-6- 
thiopyrimidine  was  melted  in  an  oil  bath  at  170°  and  treated 
with  dry  hydrogen  chloride.  The  material  quickly  solidified 
in  the  hot  bath.  It  was  then  removed  and  crystallized  from 
water,  whereupon  the  characteristic  yellow  needles  of  2,6-di- 
thiouracil  were  obtained. 

It  was  also  found  that  when  2-ethylmercapto-6-oxypyrimidine 
was  treated  in  the  same  manner  2-thiouracil  was  formed.2 

Action  of  Chloracetic  Acid  on  2,6-Dithiouracil:  Pyrimidine- 

N  =  CSCH2C02H 

2,6-dithioglycollic   Acid,  HCO2CH2SC       CH  .—Two 

II         II 
N  -  CH 

grams  of  2,6-dithiouracil  were  dissolved  in  hot  water  and  5 
grams  of  chloracetic  acid  were  added.  The  solution  was 
evaporated  to  dryness,  the  residue  taken  up  in  water  and 

1  J.  Biol.  Chem.,  3,  287  (1907). 

2  See  also  Wheeler  and  Liddle:  J.  Am.  Chem.  Soc.,  30,  1157  (1908). 


558  Wheeler  and  Liddle. 

evaporated  again,  the  operation  being  repeated  several  times 
or  until  the  yellow  color  disappeared.  The  residue  was  then 
moderately  soluble  in  alcohol  and  very  difficultly  soluble  in 
hot  water.  It  was  crystallized  from  600  cc.  of  boiling  water, 
and  2  grams  of  white  powder  separated.  Boiling  with  water 
or  even  warming  with  concentrated  hydrochloric  acid  did  not 
desulphurize  this  substance.  When  heated  it  decomposed 
above  200°. 

Calculated  for 
C8H804N2S2.  Found. 

N  10.77  11.14 

NEW  HAVEN,  CONN.. 
September,  1908. 


[Reprinted  from  The  American  Chemical  Journal, 
Vol.  XU.    No.  i.    January,  1909.] 

[Contributions  from  the  Sheffield  Laboratory  of  Yale  University.] 

CLXV.— RESEARCHES  ON  PYRIMIDINES: 

ON  THE  FORMATION  OF  PURINE  DERIVATIVES  FROM 

4-METHYLCYTOSINE. 

[FORTY-FIRST  PAPER.] 

BY  CARL  O.  JOHNS. 

It  was  found  by  Gabriel  and  Colman  that  4-methyl-6- 
ammopyrimidine1  and  2-chlor-4-methyl-6-aminopyrimidine2  did 
not  give  the  expected  5-nrtro  compounds  when  nitrated,  but 
instead  yielded  6-nitramine  derivatives. 

When  4-methylcytosine,  I.,3  is  nitrated  in  the  presence  of 
sulphuric  acid,  an  almost  quantitative  yield  of  4-methyl-5- 
nitrocytosine,  II.,  is  obtained.  To  determine  whether  the 
compound  formed  was  a  6-nitramine  or  a  5-nitropyrimidine, 
the  nitration  product  was  heated  with  30  per  cent  sulphuric 
acid  in  a  sealed  tube.  This  treatment  gave  Behrend's  ni- 
tromethyluracil,4  III.,  in  which  the  nitro  group  occupies  position 
5.  This  result  agrees  with  previous  observations  made  when 
pyrimidines  containing  an  amino  group  in  position  6  have 
been  heated  with  sulphuric  acid.  When  cytosine5  was  heated 
with  20  per  cent  sulphuric  acid  it  gave  uracil,  and  when  nitro- 
cytosine6  was  heated  under  similar  conditions,  nitrouracil 
was  formed. 

The  reduction  of  4-methyl-5-nitrocytosine  to  2-oxy-4- 
methyl-5,6-diaminopyrimidine,  IV.,  presented  considerable 
difficulty.  This  was  not  unexpected  since  it  was  only  after 
many  unsuccessful  attempts  that  2-oxy-5,6-diaminopyrimi- 
dine7  was  obtained  by  the  reduction  of  5-nitrocytosine. 

An  attempt  to  reduce  4-methyl-5-nitrocytosine  with  stan- 
nous  chloride  did  not  give  the  desired  diaminopyrimidine, 
and  when  ammonium  sulphide  was  used,  4-methylcytosine 

1  Ber.  d.  chem.  Ges.,  34,  1240  (1901). 

2  Ibid.t  34,  1241  (1901). 

8  THIS  JOURNAL,  40,  348  (1908). 

4  Ann.  Chem.  (Liebig),  240,  3  (1887). 

*  Wheeler  and  Johnson:  THIS  JOURNAL,  29,  494  (1903). 

8  Johnson,  Johns,  and  Heyl:  Ibid.,  36,  116  (1906). 

'  Ibid.,  36,  170  (1906). 


Researches  on  Pyrimidines.  59 

was  regenerated.  The  reduction  was  finally  accomplished  by 
the  use  of  aluminium  amalgam.  Even  then  prolonged  re- 
duction or  a  temperature  above  45°  liberated  ammonia  and 
regenerated  4-methylcytosine.  If  the  solution  which  was 
obtained  from  the  reduction  was  evaporated  on  a  water  bath 
at  100°  a  black  residue  was  obtained.  The  evaporation  was 
therefore  carried  out  under  diminished  pressure.  When  the 
solution  had  been  concentrated  to  a  small  volume,  stout,  flat 
crystals  of  the  2-oxy-4-methyl-5,6-diaminopyrimidine  sepa- 
rated. These  contained  one  and  one-half  molecules  of  water 
of  crystallization.  Ttiey  could  be  recrystallized  from  water 
without  undergoing  decomposition  and  then  separated  in 
long  prisms  that  contained  but  one  molecule  of  water.  It  is 
probable  that  the  decomposition  observed  when  the  solution 
obtained  from  the  reduction  was  evaporated  was  due  to  the 
presence  of  some  unstable  by-product. 

Gabriel  and  Colman  condensed  urea1  and  thiourea2  with 
4-methyl-5,6-diaminopyrimidine  and  obtained  purine  deriva- 
tives. 

The  writer  has  found  that  2-oxy-4-methyl-5,6-diaminopyrim- 
idine  also  condenses  with  urea  and  thiourea  to  give  2,8- 
dioxy-6-methylpurine,  V.,  and  2-oxy-6-methyl-8-thiopurine, 
VI.  Moreover,  formic  acid  acts  on  2-oxy-4-methyl-5,6- 
diaminopyrimidine  and  produces  a  monoformyl  derivative. 
This  compound  gives  a  sodium  salt  which  loses  water,  when 
heated,  and  yields  2-oxy-6-methylpurine,  VII. 

These  reactions  with  urea  and  formic  acid  are  such  as  might 
be  expected  of  an  orthodiamine  but  not  of  a  hydrazine  deriva- 
tive, and  they  confirm  the  assumption  that  4-methylcytosine 
nitrates  in  position  5. 

Bmil  Fischer3  has  called  attention  to  the  fact  that  the  in- 
troduction of  oxygen  into  purine  decreases  its  solubility  in 
water.  In  accordance  with  this,  2-oxy-6-methylpurine  is 
easily  soluble  in  hot  water  while  the  same  purine  with  oxygen 
or  sulphur  in  position  8  is  almost  insoluble. 

If   2-oxy-5,6-diaminopyrimidine  were   heated   with   urea  it 

1  Ber.  d.  chem.  Ges.,  34,  1247  (1901). 
*  Ibid.,  34,  1248  (1901). 
t        *  Untersuchungen  in  der  Puringruppe,  p.  74. 


6o 


Johns. 


might  be  expected  to  yield  2,8-dioxypurine.  This  compound 
is  the  only  one  of  the  three  possible  dioxypurines  which  has 
not  been  prepared  and  it  has  the  structure  which  was  at  first 
assigned  to  xan thine.  Later,  Emil  Fischer  showed  that  xan- 
thine  was  2,6-dioxypurine.1  6,8-Dioxypurine  has  been  pre- 
pared by  Fischer  and  Ach.2  The  writer  has  begun  work  on 
the  synthesis  of  2,8-dioxypurine. 


N=CNH2 

I  I 

OC          CH 

I  II 

NH C.CH8 

I. 


N: 


:CNH2 

I      I 

OC          CNO, 

I  II 

NH C.CH3 

II. 


N 


CNHa 

I  I 

OC  CNH2 

NH  --  C.CH3 

IV. 


NH CO 


I 
OC 


CNO, 


NH C.CH, 

III. 


NH C.CH3 


OC 

N 


C— NH 
C—  NH 


V. 


NH C.CH3 

I  II 

OC  C— NH 


^>co 

NH  N=C— 


NH 


NH C.CH3 

I  II 

OC 


N: 


VI. 

EXPERIMENTAL  PART. 


VII. 


C— NH 

>CH 
C— NH 


N  = 

I  I 

4-M  ethyl- 5-nitrocytosine,  OC  CNO2. — Four  grams  of  4- 

I  II 

NH C.CH3 

methylcytosine  were  dissolved  in   1 1   cc.   of  concentrated  sul- 
phuric acid.     Heat  was  liberated.     While  the  solution  was  still 

1  Ber.  d.  chem.  Ges.,  30,  553  (1897). 

2  Ibid.,  30,  2218  (1897). 


Researches  on  Pyrimidines.  61 

warm  n  cc.  of  nitric  acid,  density  1.5,  were  added  gradually. 
The  first  portions  of  nitric  acid  produced  considerable  heat 
but  no  red  fumes  were  evolved.  The  resulting  solution  was 
allowed  to  stand  at  room  temperature  for  10  minutes  and  was 
then  poured  into  100  cc.  of  cold  water.  When  the  acids  were 
neutralized  with  ammonium  hydroxide,  4.8  grams  of  a  yellow 
precipitate,  which  corresponds  to  90  per  cent  of  the  calculated 
yield,  separated.  This  compound  was  difficultly  soluble  in 
boiling  water  and  crystallized  in  small  pointed  prisms.  Its 
slight  solubility  in  water  showed  that  it  was  not  4-methyl- 
cytosine.  It  began  to  turn  brown  at  260°  and  became  black 
at  280°  but  did  not  melt.  It  was  soluble  in  acids  and  ammonia. 
Analysis  (Kjeldahl) : 

Calculated  for 

C6H6O8N4.  Found. 

N  32-94  33-17 

The  position  of  the  nitro  group  was  determined  as  follows: 
One  gram  of  the  nitro  compound  was  dissolved  in  20  cc.  of 
30  per  cent  sulphuric  acid  and  heated  in  a  sealed  tube  at  130°- 
140°  for  two  hours.  A  deposit  of  large  crystals  was  obtained 
when  the  tube  cooled.  These  were  filtered  off  and  the  filtrate 
was  analyzed  for  nitrogen  in  the  form  of  ammonia  by  adding 
sodium  hydroxide  and  distilling  into  N/io  hydrochloric  acid. 

»N   calculated   for   one   NH2   group,  0.08  gram. 
Found,  0.09  gram. 

The  crystals  which  were  filtered  off  dissolved  readily  in  boiling 
water  and  separated  from  the  cold  solution  in  stout  prisms 
and  toothed  structures.  They  possessed  all  the  properties 
of  Behrend's  nitromethyluracil,  in  which  the  nitro  group 
occupies  position  5. 

Calculated  for 

C5H5O4N3.  Found. 

N  24.56  24.99 

N=CNH2 

I  I 

2-Oxy-4-methyl-5,6-diaminopyrimidine,  OC          CNH2. — Two 

NH C.CHS 

and  two-tenths  grams  of  finely  pulverized  4-methyl-5 -nitro- 


62  Johns. 

cytosine  were  suspended  in  100  cc.  of  water  and  reduced 
vigorously  with  i  gram  of  aluminium  amalgam  for  one-half 
hour.  The  temperature  was  kept  below  45°.  The  aluminium 
used  was  in  the  form  of  fine  drillings.  The  aluminium  hy- 
droxide formed  was  filtered  off  by  suction  and  washed  with 
hot  water.  The  filtrate  was  concentrated  under  diminished 
pressure  to  about  15  cc.  -Crystals  separated  during  the  evap- 
oration. These  were  redissolved  by  careful  heating  and  a 
slight  insoluble  residue  was  filtered  off.  Stout,  flat  prisms 
separated  on  cooling.  These  became  brown  above  250°  and 
decomposed  slowly  at  about  28o°-285°  without  melting. 
They  contained  one  and  one-half  molecules  of  water  of  crystal- 
lization. The  yield  of  pure  hydrous  crystals  was  from  50  to 
60  per  cent  of  the  calculated.  Water  determinations  on  crystals 
obtained  from  different  experiments  gave  the  following  results: 
I.  1.6340  gram  lost  0.2637  gram  of  H2O. 
II.  0.5011  gram  lost  0.0805  gram  of  H2O. 
III.  1.1859  gram  lost  0.1907  gram  of  H2O. 

Calculated  for  Found. 

C6H8ON4.iiH2O.  I.  II.  III. 

H2O  16.16  16.14         16.06         16.08 

Nitrogen  determinations  resulted  as  follows : 

Calculated  for 
C5H8ON4.iiH8O.  Pound. 

N  33-53  33.6i 

Calculated  for 

C6H8ON4.  Found. 

N  40.00  39-78 

When  the  flat  crystals  obtained  above  were  recrystallized 
from  water  they  separated  in  long  prisms  that  contained  but 
one  molecule  of  water  of  crystallization.  The  following 
analyses  were  made  on  different  lots  of  the  recrystallized 
diaminopyrimidine. 

Calculated  for  Found. 

C5H8ON4.HjO.  I.  II.  III. 

H2O    11.39       n-53    JI-49    11.42 

Calculated  for 

C6H8ON4.  Found. 

N  40 . oo  40 . 02 


Researches  on  Pyrimidines.  63 

2-Oxy-4-methyl-5,6-diaminopyrimidine  was  easily  soluble 
in  hot  water  but  it  dissolved  only  slightly  in  cold  water.  It 
did  not  dissolve  in  alcohol.  The  dried  crystals  were  very 
hygroscopic.  Water  solutions  gave  precipitates  with  mercuric 
chloride  and  picric  acid.  The  picrate  charred  above  240° 
but  did  not  melt.  The  best  yield  was  obtained  by  using  fine 
aluminium  drillings  and  reducing  rapidly.  If  the  reduction 
is  prolonged  or  the  temperature  raised  above  45°,  ammonia  is 
liberated  and  4-methylcytosine  is  re-formed. 

NH  -  C.CH3 

I  II 

2,8-Dioxy-6-methylpurine,  OC          C  —  NH.  —  One  gram  of  an- 

I      t   >co 

N=C—  NH 

hydrous  2-oxy-4-methyl-5,6-diaminopyrimidine  was  intimately 
mixed  with  i  gram  of  urea  by  grinding  in  a  mortar.  This 
mixture  was  heated  in  an  oil  bath  kept  at  I7o°-i8o°  for  one- 
half  hour.  The  mass  melted  and  ammonia  was  evolved.  The 
fusion  product  was  dissolved  in  boiling  water  containing  a  few 
drops  of  ammonium  hydroxide  and  the  solution  was  decolorized 
with  animal  charcoal.  When  the  filtrate  was  boiled  to  drive 
off  ammonia,  minute  crystals  separated.  These  were  almost 
insoluble  in  boiling  water  but  dissolved  readily  in  mineral 
acids  and  bases.  They  were  insoluble  in  alcohol  or  acetic  acid. 
They  did  not  melt  at  345°.  The  yield  was  i.i  grams,  or  93 
per  cent  of  the  calculated  weight. 

Calculated  for  Found. 

C6H602N4.  I.  II. 

N  33-73  33-59  33-8i 

NH  --  C.CH3 

I  II 

2-Oxy-6-methyl-8-thiopurine,  OC          C  —  NH.  —  One-half  gram 


N=C—  NH 

of  2-oxy-4-methyl-5,6-diaminopyrimidine  was  ground  in  a 
mortar  with  one  gram  of  thiourea.  The  mixture  was  heated 
in  an  oil  bath  kept  at  i8o°-i9o°  for  one  hour.  It  melted  and 


64  Johns. 

turned  black.  Ammonia  was  evolved.  The  fusion  mass  was 
dissolved  in  water  containing  ammonium  hydroxide.  A  clear 
solution  was  obtained  by  using  animal  charcoal.  This 
solution  gave  an  immediate  precipitate  when  acidified  with 
acetic  acid.  The  compound  thus  obtained  was  purified  by 
dissolving  in  very  dilute  ammonium  hydroxide  and  reprecipi- 
tating  with  acetic  acid.  Extremely  small  crystals  were  ob- 
tained. These  were  not  soluble  in  alcohol  and  were  almost 
insoluble  in  boiling  water  and  boiling  acetic  acid.  They  were 
freely  soluble  in  alkalies  and  mineral  acids.  They  did  not 
melt  at  345°.  The  yield  of  the  pure  purine  was  80  per  cent 
of  the  calculated  quantity. 

Calculated  for 
CeH6ON4S.  Found. 

N  30.77  30.90 

S  17.59  17-81 

The  Monoformyl  Derivative  of  2-Oxy-4-methyl-5,6-diami- 
nopyrimidine,  C5H7ON4.CHO. — Four  grams  of  the  diamino- 
pyrimidine  were  dissolved  in  4  cc.  of  formic  acid,  density  1.2, 
and  the  solution  was  heated  on  a  water  bath  for  one-half  hour. 
The  excess  of  formic  acid  was  evaporated  in  an  open  dish  and 
the  residue  was  dissolved  in  water.  When  this  solution  was 
neutralized  with  ammonium  hydroxide,  the  monoformyl 
derivative  precipitated.  It  was  moderately  soluble  in  hot 
water  and  formed  minute  crystals  when  the  solution  was 
cooled.  It  dissolved  readily  in  acetic  acid  and  was  slightly 
soluble  in  boiling  alcohol.  The  crystals  began  to  turn  black 
at  about  325°  but  did  not  melt  at  345°. 

Calculated  for 

C6H802N4  Found. 

N  33-33  33-29 

Prolonged  heating  in  an  oil  bath  at  240°  caused  the  formyl 
derivative  to  darken  considerably  but  it  did  not  lose  water  to 
form  a  purine.  When  recrystallized  from  water  the  heated 
product  exhibited  all  the  properties  of  the  formyl  derivative. 
It  was  dried  at  130°  for  analysis. 

Calculated  for 

C6H8OaN4.  Found. 

N  33-33  33-46 


Researches  on  Pyrimidines.  65 

NH C.CH3 

I  II 

2-Oxy-6-methylpurine,  OC          C — NH. — Three  grams  of  the 

-     ';     •  -  ]=J-N 

monoformyl  derivative  of  2-oxy-4-methyl-5,6-diaminopyrimi- 
dine  were  dissolved  in  an  excess  of  10  per  cent  solution  of  sodium 
hydroxide.  When  alcohol  was  added  the  sodium  salt  of  the 
formylpyrimidine  separated  as  a  white  powder.  This  salt  was 
dried  and  heated  in  an  oil  bath  at  200°.  Water  came  off 
readily  and  considerable  foaming  ensued,  leaving  a  porous 
crust.  This  dissolved  freely  in  cold  water  and  did  not  give  a 
precipitate  when  the  solution  was  neutralized  with  acetic  acid. 
The  solution  was  therefore  evaporated  to  dryness  and  the 
residue  was  dissolved  in  a  little  hot  water.  Clusters  of  slender 
prisms  were  obtained  when  the  solution  cooled  slowly.  These 
turned  brown  at  about  280°  and  became  black  above  300° 
but  did  not  melt  at  345°.  They  were  easily  soluble  in  acetic 
acid  and  ammonium  hydroxide  and  sparingly  soluble  in  boiling 
alcohol.  A  water  solution  gave  a  precipitate  with  mercuric 
chloride  but  did  not  give  precipitates  with  ferric  chloride,  copper 
sulphate,  or  chloroplatinic  acid. 

Calculated  for  Found. 

C<,H6ON4.  I.  II.  III. 

N  37-33  37-05         37.10        37.35 

NEW  HAVEN,  CONN., 
November,  1908. 


[Reprinted  from  the  Journal  of  The  American  Chemical  Society, 
Vol.  XXXI.     No.  5.      May,  1909  ] 


[CONTRIBUTIONS  FROM  THE  SHEFFIELD  LABORATORY  OF  YALE  UNIVERSITY.] 

RESEARCHES    ON    PYRIMIDINES:     SYNTHESIS   OF    i-METHYL-5- 

HYDROXYURACIL. 

[FORTY-SECOND  PAPER.] 

BY  TREAT  B.  JOHNSON  AND  I).  BREESE  JONES 
Received  March  19,  1909. 

In  a  previous  paper  from  this  laboratory,  Johnson  and  McCollum1 
described  a  new  synthesis  of  5-hydroxyuracil  (isobarbituric  acid).  They 
showed  that  this  pyrimidine  is  formed  quantitatively  by  hydrolysis  of 
2-ethylmercapto-5-ethoxy-6-oxypyrimidine  with  hydrochloric  acid.  In 
a  recent  paper,  Johnson  and  Jones2  have  shown  that  nitrogen-alkyl 
derivatives  of  this  mercaptopyrimidine  can  be  obtained  easily  and  also 
undergo  hydrolysis,  giving  nitrogen-alkyl  derivatives  of  5-hydroxyuracil. 
They  prepared  by  this  method  i-  and  3-benzyl-5-hydroxyuracils,  I., 
and  II. 

CeH5CH2N CO  NH  — CO 

i       I  II 

CO      COH  CO      COH 

I  II  I  II 

NH— CH  C8H5CH2N CH 

I.  II. 

The  object  of  the  work  described  in  this  paper  was  to  prepare  the 
nitrogen-methyl  derivatives  of  2-ethylmercapto-5-ethoxy-6-oxypyrimidine3 
and  study  their  behavior  on  hydrolysis. 

5-Hydroxyuracil  and  nitrogen-alkyl  derivatives  of  this  pyrimidine 
are  prepared,  according  to  BehrendV  synthesis,  by  the  reduction  of 
5-nitrouracil  and  its  alkyl  derivatives  with  tin  and  hydrochloric  acid. 
The  only  nitrogen-alkyl  derivatives  of  5-hydroxyuracil  that  have  been 
synthesized  by  this  method,  are  methyl-5-hydroxyuracil  (methyliso- 
barbituric  acid)  and  ethyl-5-hydroxyuracil  (ethylisobarbituric  acid). 
These  pyrimidines  are  incorrectly  represented  in  Beilstein's  Handbuch5 
as  i-alkyl  pyrimidines  III,  and  IV,  and  were  prepared  by  Lehmann8 
by  reducing  methyl-  and  ethylnitrouracils,  to  which  he  assigned,  without 
proof,  formulas  V,  and  VI. 

1  J.  Biol.  Chem.,  i,  437. 

2  Am.  Chem.  J.,  40,  538. 

3  Loc.  cit. 

4  Ann.,  249,  39;  Ibid.,  251,  239. 
8  Vol.  I,  1347,  1348- 

8  Ann.,  253,  77. 


SYNTHESIS   OF    I-METHYIv-5-HYDROXYURACIL.  591 

CHSN CO          C2H5N CO          CH3N CO          C,H6N CO 

COH  CO      CNO3  CO      CNO, 


NH— CH  NH— CH  NH— CH 

IV.  V.  VI. 

The  structures  of  these  alkyl  nitrouracils,  and  consequently  the  corre- 
sponding 5-hydroxyuracils  of  Lehmann's  were  correctly  established  by 
Behrend  and  Thurm1  who  showed  that  they  are  to  be  represented  as 
3-alkyl-pyrimidines ;  for  example,  3,4-dimethyluracil  (a-dimethylur- 
acil),  VII,  and  nitric  acid  reacted  giving  the  same  nitromethyluracil, 
VIII,  as  originally  was  obtained  by  Lehmann2  by  methylation  of  nitro- 
uracil.  Furthermore,  the  oxidation  of  Lehmann's  methyl-5-hydroxy- 
uracil  with  bromine  water  gave  a  methylisodialuric  acid,  IX,  which 
condensed  with  urea,  giving  3-methyluric  acid  (d-acid)  X.3  Lehmann's 

NH— CO  NH— CO  NH— CO  NH— CO 


CO      CH               CO      CNO2  CO      COH           CO     CNH> 

II                              II  I          II                   II 

CCH3  CH3N CH        CH3N COH  CH3N ( 

VII.                            VIII.  IX.                                X. 


CO      CNHV 

I       II     >co 

[N CNH/ 


ethylnitrouracil  reacted  with  methyl  iodide,  giving  the  same  ethylmethyl- 
pyrimidine  as  was  obtained  from  i-methylnitrouracil  and  ethyl  iodide.4 

Johnson  and  Jones5  observed  that  i-benzyl-2-ethylmercapto-5-ethoxy- 
6-oxypyrimidine  is  the  chief  product  of  the  reaction  when  benzyl  chloride 
acts  on  2-ethylmercapto-5-ethoxy-6-oxypyrimidine,  XI,  in  presence  of 
alkali.  We  now  find  that  methyl  iodide  reacts  with  this  mercaptopyrim- 
idine,  giving  a  mixture  of  the  corresponding  i  and  3-methylpyrimi- 
dines  which  contains  about  70  per  cent,  of  the  theoretical  yield  of  i- 
methyl-2-ethylmercapto-5-ethoxy-6-oxypyrimidine,  XII. 

2-Ethylmercapto-3-methyl-5-ethoxy-6-oxypyrimidine,  XVI,  possessed 
the  unique  property  of  combining  with  potassium  iodide,  giving  a  definite, 
double  compound.  We  suspected  this  substance,  at  first,  of  being  an 
addition  product  of  methyl  iodide  and  the  potassium  salt  of  i-  or  3- 
methyl-2-ethylmercapto-5-ethoxy-6-oxypyrimidines.  This  assumption, 
however,  proved  to  be  incorrect,  since  the  same  compound  was  formed 
quantitatively  by  crystallizing  2-ethylmercapto-3-methyl-5-ethoxy-6-oxy- 
pyrimidine  from  an  alcoholic  solution  of  potassium  iodide.  The  analytical 
determinations  agreed  with  the  calculated  values  for  a  double  compound 

Ann.,  323,  160. 
Loc.  cit. 

E.  Fischer  and  Ach,  Ber.,  32,  2721.     Loeben,  Ann.,  298,  181.     Behrend  and 
Dietrich,  Ann.,  309,  260. 

Behrend  and  Thurm,  Loc.  cit. 
Loc.  cit. 


592 


ORGANIC  AND  BIOLOGICAL. 


containing  3  molecules  of  the  3-methylpyrimidine  and  2  molecules  of 
potassium  iodide,  XIII. 

2-Bthylmercapto-i-methyl-5-ethoxy-6-oxypyrimidine,  XII,  is  converted 
smoothly  into  i-methyl-5-ethoxyuracil,  XV,  by  digestion  with  hydro-) 
chloric  acid.  When  this  pyrimidine  or  the  mercaptopyrimidine  are  heated 
with  strong  hydrochloric  acid  at  120-130°,  they  are  changed  practically 
quantitatively  into  i-methyl-5-hydroxyuracil,  XVII.  Hydrolysis  of 
2-ethylmercapto-i-methyl-5-ethoxy-6-oxypyrimidine  with  boiling  hydro- 
bromic  acid  gave  a  mixture  of  i-methyl-2-thio-5-hydroxyuracil,  XIV, 
and  i-methyl-5-ethoxyuracil,  XV.  The  formation  of  2-thiopyrimidines 
from  the  corresponding  mercapto  derivatives  by  hydrolysis  with  acids 
has  previously  been  observed  by  Johnson  and  Clapp;1  for  example, 
2-ethylmercapto-3,5-dimethyl-6-oxypyrimidine  gave  2-thio-3,5-dimethyl- 
6-oxypyrimidine  when  digested  with  hydrobromic  acid. 

The  sulphur  in  2-thio-i-methyl-5-hydroxy-6-oxypyrimidine,  XIV,  is 
very  firmly  bound.  It  cannot  be  removed  by  digestion  with  chloracetic 
acid.2  The  pyrimidine  combines  with  this  acid,  giving  i -me  thy  1-2- 
thioglycollic-acid-5-hydroxy-6-oxypyrimidine  which  can  be  digested 
with  concentrated  hydrochloric  acid  without  decomposition.  When  the 
double  compound  of  2-ethylmercapto-3-methyl-5-ethoxy-6-oxypyrimidine 
and  potassium  iodide,  XIII,  was  digested  with  hydrochloric  acid,  it  was 
converted  into  2-thio-3-methyl-5-ethoxy-6-oxypyrimidine,  XVIII. 

CH3N— CO  NH— CO  ~          N— CO 


COC2H5  «—  C^SC 


C2H5SC    COC2H5 

II      II 
CH3N— CH 

XIII. 


.  2KI 


_     3 


CH3N CO 

CO      CO( 


N— CO 

II      I 
C2H5SC 

I      II 
CH3N— CH 

JXVL 

NH— CO 

I          I 
CS      COC2H& 

I          II 
CH3N CH 

XVIII. 


1  Jour.  Biolog.  Chem.,  5,  57. 

2  Wheeler  and  Liddle,  Am.  Chem.  /.,  40,  547. 


SYNTHESIS   OF    I-METHYV5-HYDROXYURACII,.  593 

Summary. 

1.  Alkylation  of  5-nitrouracil  with  methyl  iodide  gives  chiefly  3-methyl- 
5-nitrouracil.     Reduction    of    this    nitropyrimidine    gives    3-methyl-5- 
aminouracil  and  j-methyl-j-hydroxyuracil, 

NH— CO 

CO      COH. 

I        I! 

CH3N CH 

2.  Alkylation      of      2-ethylmercapto-5-ethoxy-6-oxypyrimidine      with 
methyl    iodide    gives    chiefly    i-methyl-2-ethylmercapto-5-ethoxy-6-oxy- 
pyrimidine.     Hydrolysis  of  this  mercaptopyrimidine  with  hydrochloric 
acid  at  120-130°  gives  quantitatively  i -methyl- j-hydroxyuracti, 

CH3N CO 

CO      COH. 


NH— \ 


-CH 
Experimental  Part. 

The  2-ethylmercapto-5-ethoxy-6-oxypyrimidine  that  was  used  in  this  work  was 
prepared  from  ethyl  formate  and  ethyl  ethylglycollate  according  to  the  directions  of 
Johnson  and  McCollum.1  This  pyrimidine  can  be  obtained  easily  in  good  yield  by 
this  method.  The  yields  of  pyrimidine  obtained  in  five  different  condensations  are 
given  in  the  following  table: 

if  i 

I     f .      I  I 

£  tj  Grams  of  pyrimidine  obtained,  *g 

H  £  NH— CO 

w9>  «  «<£  I          I 

aw  a  aw  c2H6sc     coc2H6.  % 


2o  2  23  II        II  53 

O  CO  N CH  £ 

1  113  75  79-5  42-0  48.8 

2  102  65  71.8  35.0  45.1 

3  109  70  76.7  44.5  53.6 

4  76  50  53-5  27.5  47.5 

5  76  50  53-5  32.0  55.3 

CH3N  — CO 

I        I 
i- Methyl-2-ethylmercapto-5-ethoxy-6-oxy pyrimidine,       C2H6S.C      COC2H6.  —  Fifteen 

I!      II 

N— CH 

grams  of  2-ethylmercapto-5-ethoxy-6-oxypyrimidine1  and  4.5  grams  (i  mol.)  of  pul- 
verized potassium  hydroxide  were  dissolved  in  150  cc.  of  boiling,  absolute  alcohol. 
Fourteen  grams  of  methyl  iodide  were  then  added  and  the  mixture  warmed,  in  a  water- 
bath,  until  it  gave  no  alkaline  reaction,  when  tested  with  moistened  turmeric  paper 
(45  minutes).  After  cooling,  the  insoluble  potassium  iodide  (u  grams)  was  filtered 
1  Loc.  cit. 


594  ORGANIC  AND  BIOLOGICAL. 

off  and  the  excess  of  alcohol  expelled  by  evaporation  under  diminished  pressure.  This 
method  of  procedure  was  adopted  after  we  had  observed,  in  a  preliminary  experiment, 
that  the  methyl  pyrimidine  volatilized  with  alcohol  vapors  by  distillation  at  ordinary 
pressure.  We  obtained  a  crystalline  substance  which  was  extracted  several  times 
with  an  excess  of  ether  and  the  insoluble  part  saved  (see  below).  After  evaporation 
of  the  ether  we  obtained  u.o  grams  of  the  i-methylpyrimidine  melting  at  45-50°. 
This  yield  corresponds  to  about  69  per  cent,  of  the  theoretical. 

In  a  second  experiment  10.0  grams  of  2-ethylmercapto-5-ethoxy-6-oxypyrimidine 
and  2.85  grams  of  potassium  hydroxide  were  dissolved  in  100  cc.  of  boiling,  absolute 
alcohol  and  the  solution  cooled  to  10°.  Ten  and  six- tenths  grams  of  methyl  iodide 
(1.5  mols.)  were  then  added  and  the  solution  allowed  to  stand  at  20-5°.  Potassium 
iodide  began  to  separate  in  one-half  an  hour  and  after  3  hours  the  reaction  was  com- 
plete. The  weight  of  undissolved  potassium  iodide  was  6.25  grams.  After  evapora- 
tion of  the  alcohol  at  40-50°  at  47  mm.  pressure  the  residue  was  then  extracted,  as 
usual,  with  an  excess  of  ether.  The  yield  of  i-methylpyrimidine  corresponded  to 
about  71  per  cent,  of  the  theoretical.  The  product  insoluble  in  ether  was  saved  (see 
below). 

The  2 -ethylmercapto- i-methylpyrimidine  is  extremely  soluble  in  ethyl  alcohol,  ben- 
zene and  acetone.  It  crystallized  from  ether  and  water  in  plates  melting  at  50°  to  a 
clear  oil.  Analysis  (Kjeldahl): 

Calculated  for  C9H14O2N2S:  N  13.08;  found,  13.4,  13.20. 

The  Material  Insoluble  in  Ether. — This  substance  was  extremely  soluble  in  water  and 
difficultly  soluble  in  cold  alcohol.  It  crystallized  from  a  saturated,  aqueous  solution 
in  characteristic  needles  arranged  in  the  form  of  rosettes  and  from  95  per  cent,  alcohol 
in  well-developed  prisms.  It  decomposed,  when  heated  slowly,  at  177-8°  into  an  oil 
and  a  crystalline  substance,  which  did  not  melt  below  250°.  The  compound  con- 
tained sulphur  and  iodine  and  left  an  inorganic  residue  when  fused  on  platinum  foil. 
When  some  of  the  compound  was  dissolved  in  cold  water,  and  silver  nitrate  solution 
added,  a  gelatinous,  white  silver  salt  separated  which  decomposed,  when  the  solution 
was  warmed,  giving  yellow  silver  iodide.  The  crystalline  habit  and  characteristic 
properties  indicated  that  we  were  dealing  with  a  definite  compound  and  not  a  mixture 
of  a  pyrimidine  and  potassium  iodide.  Our  analytical  determinations  agreed  with  the 
calculated  values  in  a  double  compound  containing  3  molecules  of  2-ethylmercapto-^- 
methyl-5-ethoxy-6-oxypyrimidine  and  2  molecules  of  potassium  iodide,  (C9H14O2N2S)3.2KI. 

Calculated:  N,  8.60  ;   I,  25.00 

Found:         N.  8.26,  8.35,  8.40;  I,  24.55 

N  — CO 

II        I 
2-Ethylmercapto-3-methyl-5-ethoxy-6-oxypyrimidinet  C2H5SC — COC2H5. — Some  of  the 

I       II 
CH3N— CH 

double  compound  (above)  was  heated,  in  an  oil  bath,  at  175-90°  for  about  30  minutes. 
We  obtained  a  crystalline  substance,  on  cooling,  which  was  thoroughly  pulverized  and 
digested  for  a  long  time  with  an  excess  of  anhydrous  ethyl  acetate.  After  expelling 
the  excess  of  ethyl  acetate  at  100°,  we  obtained  a  crystalline  substance  which  was 
extremely  soluble  in  cold  water  and  alcohol.  It  crystallized  from  ethyl  acetate  in 
clusters  of  small  prisms  melting  at  149-51°.  They  were  free  from  iodine  but  gave  a 
strong  test  for  sulphur.  The  compound  slowly  sublimed  when  heated  at  100°.  A 
mixture  of  the  pyrimidine  and  2-ethylmercapto-5-ethoxy-6-oxypyrimidine1  (melting 
1  Loc.  cit. 


SYNTHESIS   OF    I-METHYIv-5-HYDROXYURACIIv.  595 


at  169°)  melted  at  118-25°.  Analysis  (Kjeldahl):  Calculated  for  C^O^S,  N 
13.0;  found,  13.4. 

Crystallization  to/  2-Ethylmercapto-3-methyl-5-ethoxy-6-oxypyrimidine  from  an  Alco- 
holic Solution  of  Potassium  Iodide.  —  About  0.5  gram  of  the  pyrimidine  was  dissolved 
in  25  cc.  of  hot,  absolute  alcohol,  which  had  previously  been  saturated  with  potassium 
iodide.  On  cooling,  the  double  compound,  described  above,  separated  in  colorless 
prisms  which  decomposed  at  178°.  Analysis  (Kjeldahl):  Calculated  for  (C6H14O2N2S)3. 
2KI,  N  8.60;  found,  8.5. 

CH3.N  -  CO 

I          I 

i-Methyl-2-thio-5-hydroxyuracil,          CS      COH.  —  Three   and  five-tenths   grams  of 

I        I! 

NH—  CH 

i-methyl-2-ethylmercapto-5-ethoxy-6-oxypyrimidine  were  digested  with  20  cc.  of 
hydrobromic  acid  for  about  14  hours.  The  solution  was  then  evaporated  to  dryness, 
when  we  obtained  a  crystalline  substance  which  dissolved  in  boiling  water.  Upon 
cooling,  about  2.0  grams  of  slender  prisms  separated  which  were  extremely  insoluble 
in  cold  water  and  boiling  alcohol.  The  material  had  no  definite  melting  point  and 
gave  a  strong  test  for  sulphur.  It  crystallized  from  hot  water  without  water  of 
crystallization.  Analysis  (Kjeldahl):  Calculated  for  C5H6O2N2S,  N  17.7;  found, 

17-39,  17-5. 

CH3N  -  CO 

I  I 

i-Methyl-2,6-dioxy-5-ethoxypyrimidine,         CO      COC2H5.  —  After  separation  of  the 

I  II 

NH—  CH 

2-thiopyrimidine,  in  the  preceding  experiment,  the  aqueous  filtrate  was  evaporated 
to  dryness.  We  obtained  a  crystalline  substance  which  crystallized  from  hot  water 
in  aggregates  of  short  prisms.  They  turned  brown,  when  heated  above  220°,  and 
then  melted  to  an  oil  at  about  240°  according  to  the  rate  of  heating.  The  compound 
did  not  contain  sulphur,  and  reacted  with  diazobenzene  sulphonic  acid  giving  a  strong, 
red  color.  Analysis  (Kjeldahl):  Calculated  for  C7H10O3N2,  N  16.47;  found,  16.7. 

This  same  pyrimidine  is  obtained  smoothly  and  practically  free  from   i-methyl- 
2-thio-5-hydroxyuracil    by    digestion    of     i-methyl-2-ethylmercapto-5-ethoxy-6-oxy- 
pyrimidine  with  concentrated  hydrochloric  acid  for  several  hours. 
CH3N  -  CO 
I  I 

i-Methyl-5-hydroxyuracil,        CO       COH.  —  This  pyrimidine  was  formed  practically 

I  II 

NH—  CH 

quantitatively  when  i  -methyl-  2,  6-dioxy-5-ethoxy  pyrimidine  or  i-methyl-2-ethyl- 
mercapto-5-ethoxy-6-oxypyrimidine  was  heated  with  concentrated  hydrochloric 
acid  at  120-30°  for  2-3  hours.  The  pyrimidine  is  more  soluble  in  water  than  the 
isomeric  3-methyl-5-hydroxyuracil.1  It  dissolves  readily  in  boiling  water  and  alcohol 
and  separates  from  hot  aqueous  solutions  in  clusters  of  radiating  prisms  which  melt 
at  247°  to  an  oil  with  slight  effervescence.  The  isomeric  pyrimidine  decomposes 
above  260°  without  melting,  with  violent  effervescence.  A  mixture  of  the  i-  and 
3-methyl-5-hydroxyuracils  melted  at  217-30°  to  an  oil.  Analysis:  Calculated  for 
C6H6O3N2,  N  19.71;  found,  19.9. 

CH3N-CO 

I  I 
i~Methyl-2-thioglycollic-acid-5-hydroxy-6-oxypyrimidine,         HOOCCHjS.C     COH.  — 

II  II 
N—  CH 

1  Loc.  cit. 


596  ORGANIC  AND  BIOLOGICAL. 

Two  grams  of  chloracetic  acid  and  i  gram  of  i  -methyl- 2 -thio-5-hydroxyuracil  were 
dissolved  in  boiling  water  and  the  solution  evaporated  to  dryness.  We  obtained  a 
crystalline  compound,  which  separated  from  hot  water  in  stout  prisms,  and  decom- 
posed at  217°  with  effervescence.  It  gave  a  strong  test  for  sulphur  and  crystallized 
from  water  without  water  of  crystallization.  Analysis'  (Kjeldahl):  Calculated  for 
C7H8O4N2S,  N  1 2. 96;  found,  12.8. 

This  pyrimidine  was  extremely  stable  in  presence  of  hydrochloric  acid.  Some  of 
the  compound  was  dissolved  in  a  large  excess  of  concentrated  acid  and  the  solution 
evaporated  to  dryness.  The  pyrimidine  was  recovered  unaltered  and  decomposed 
sharply  at  217°.  Analysis  (Kjeldahl):  Calculated  for  C7H8O4N2S,  N  12.96;  found, 
12.94. 

NH-CO 
I  I 

2-Thio-3-methyl-5-ethoxy-6-oxy pyrimidine,         CS       COC2H6. — This   pyrimidine   was 

I         I! 

CH3N CH 

obtained,  in  small  amount,  when  the  double  compound  of  potassium  iodide  and  2- 
ethylmercapto-3-methyl-5-ethoxy-6-oxypyrimidine  was  digested  with  hydrochloric 
acid.  After  expelling  the  hydrochloric  acid,  we  obtained  a  crystalline  substance 
which  was  washed  with^alcohol  and  then  crystallized  from  hot  water.  It  separated 
in  long  needles^ which  melted  at  210—1°  to  an  oil,  without  effervescence.  It  con- 
tained sulphur  and  gave  a  violet  colored  solution  by  treatment  with  bromine  water  and 
barium  hydroxide.  Analysis  (Kjeldahl):  Calculated  for  C7Hi0O2N2S,  N  15.05;  found, 

15-05- 

NEW  HAVEN,  CONN. 


[Reprinted  from  The  American  Chemical  Journa 
Vol.  XLJI.    No.  i.    July,  1909.] 


[Contributions  from  the  Sheffield  Laboratory  of  Yale  University.] 

CLXVIL—    RESEARCHES  ON  PYRIMIDINES: 
THE  PREPARATION  OF  3-METHYL-  AND  3- 

BENZYLURACIL. 
[FORTY-THIRD  PAPER.] 

BY  HENRY  L.  WHEELER  AND  TREAT  B.  JOHNSON. 

From  a  theoretical  standpoint  a  larger  number  of  alkyl  com- 
pounds may  result  by  alkylating  a  uracil  derivative  than  can 
be  obtained  by  a  similar  treatment  of  a  2-mercapto-6-oxy- 
pyrimidine.  With  the  mercaptopyrimidines  only  three  mono- 
derivatives  should  result.  With  uracil,  4-methyluracil,  thy- 
mine,  or  5-methyluracil,  in  each  case  there  are  ten  possible 
compounds,  four  mono-  and  six  dialkyl  derivatives.  This 
includes  oxygen  derivatives,  but  not  tautomeric  forms.  In 
the  case  of  the  2-amino-6-oxypyrimidines,  the  guanidine 
derivatives,  the  alkylation  may  be  still  more  complicated. 

The  work  done  in  this  laboratory  has  therefore  been  con- 
fined almost  entirely  to  the  alkylation  of  mercaptopyrimidines. 
2-Ethylmercapto-6-oxypyrimidine1  and  2-ethylmercapto-5-eth- 
oxy-6-oxypyrimidine2  gave  with  potassium  hydroxide  and 
methyl  iodide  the  i -methyl  derivatives  in  largest  quantity, 
while  2-ethyl-mercapto-5-methyl-6-oxypyrimidine3  gave  a  mix- 
ture of  about  equal  amounts  of  the  i-  and  3-methylated 
products.  2-Ethylmercapto-5-ethoxy-6-oxypyrimidine4  with 
benzyl  chloride  also  gave  a  i -benzyl  derivative  as  the  chief 
product. 

On  the  other  hand  2-ethylmercapto-6-oxypyrimidine5  and 
2-ethylmercapto-5-methyl-6-oxypyrimidine  gave  mostly  3- 
alkyl  compounds  with  benzyl  chloride.  A  similar  result  was 
obtained  with  the  former  pyrimidine  and  ethyl  chloracetate.6 

Besides  the  N  isomers  there  were  probably  formed,  in  most 
of  these  cases,  some  6-oxyalkyl  derivatives  (oils),  the  amount 

1  Johnson  and  Heyl:  THIS  JOURNAL,  37    628  (1907). 

2  Johnson  and  Jones:  Ibid.,  40,  538  (1908). 

3  Johnson  and  Clapp:  J.   Biol.  Chem.,  5,  51  (1908). 

4  Johnson  and  Jones:  Loc.  cit, 

6  Johnson  and  Derby:  THIS  JOURNAL,  40,  444  (1908). 

6  Wheeler  and  Liddle:  J.  Am.  Chem.  Soc.,  30,  1152  (1908). 


Researches  on  Pyrimidines.  31 

of  6-oxy  derivative  being  noteworthy  in  the  methylation  of 
2-anilino-6-oxypyrimidine. 1 

These  examples  show  that  no  regularity  is  ^>bserved  in  the 
alkylation  of  2-mercapto-6-oxypyrirriidines,  that  analogous 
salts  can  give  different  results  with  the  same  halide,  and  that 
with  different  halides  the  salts  may  be  attacked  in  different 
positions.  It  will  also  be  noticed  from  the  above  that  the 
papers  so  far  published  have  contained  accounts  only  of  the 
results  obtained  with  2-mercapto-6-oxypyrimidines.  It  was 
therefore  of  interest  to  study  the  alkylation  of  some  isomeric 
2-oxy-6-mercaptopyrimidines  and  to  examine  the  effect  pro- 
duced when  the  mercapto  group  and  the  oxygen  atom  were 
interchanged. 

We  now  find  when  2-oxy-6-methyl-mercaptopyrimidine 
(V.)  is  treated  with  potassium  hydroxide,  in  alcoholic  solution, 
and  either  methyl  iodide  or  benzyl  chloride,  that  3-alkyl  deriva- 
tives result.  The  amount  of  isomeric  products,  if  any,  formed 
in  this  reaction  is  very  small. 

The  6-mercapto  derivatives,  like  the  2-mercapto  com- 
pounds, on  boiling  with  hydrochloric  acid  evolve  mercaptan 
and  pass  smoothly  into  uracil  derivatives.  The  new  3-methyl- 
uracil  (VII.)  thus  obtained  now  completes  the  list  of  the 
theoretically  possible  monomethyluracils.  It  gives  no  color 
with  diazobenzenesulphonic  acid  although  the  isomeric  i- 
methyluracil  gives  a  red  coloration.2 

2-Oxy-6-methylmercaptopyrimidine  (V.)  was  prepared  by 
methylating  6-thiouracil  (IV.),  while  the  preparation  of  the 
latter  substance  has  been  described  by  Wheeler  and  Liddle.3 
The  various  steps  in  the  synthesis  of  3-methyluracil  may  be 
represented  as  follows: 

1  Johnson  and  Heyl:  THIS  JOURNAL,  38,  238  (1907). 

2  Johnson  and  Clapp:  J,  Biol.  Chem.,  5,  163  (1908) 

3  THIS  JOURNAL,  40,  547  (1908). 


Wheeler  and  Johnson. 
HN CO  N=  =CC1  HN 

[5SC 


C2H5SC        CH  — >  C2H5SC         CH 


C2H 


oi 


CH 


CH3N CH 

VI. 


\ 


HN 


CH3N 

VII. 

3-Methyluracil  dissolves  in  alkali  and  is  precipitated  unaltered 
by  hydrochloric  acid. 

Miiller1  obtained  a  3-methyluracil-4-carboxylic  ester  by 
condensing  oxalacetic  ethyl  ester  and  methylurea.  When 
the  sodium  salt  of  this  substance  was  treated  with 
hydrochloric  acid  he  obtained  /?-methyluramidoacrylic  acid, 
H2N  —  CO  —  N(CH3)CH  =  CHCOOH.  Neither  acids  nor  al- 
kalies changed  this  substance  into  3-methyluracil. 

Similar  peculiar  relations  have  been  observed  before  in  the 
pyrimidine  series.  Fischer  and  Roeder2  in  their  synthesis 
of  uracil  obtained  an  acid  which  differed  from  uracil  by  one 
molecular  proportion  of  water.  It  was  left  undecided  whether 
this  substance  was  uracilic  acid  (Uracilsaure) ,  H2N  —  CO  — 
NHCH  =  CHCOOH,  or  oxyhydrouracil, 


HN  —  CO  —  NH  —  CH2  —  CHOHCO.     They    did    not    suc- 
ceed in  converting  the  substance  into  uracil. 

Johnson   and   Clapp3   obtained    two    a-methyl-/9-guanidine- 
acrylic  acids.     One  could  be  dissolved  in  dilute  alkali  and  be 


1  J.  prakt.  Chem.,  56,  498  (1897). 

2  Ber.  d.  chem.  Ges.,  34,  3760  (1901). 

3  THIS  JOURNAL,  32,  130  (1904). 


Researches  on  Pyrimidines.  33 

reprecipitated  by  acids  unaltered,  with  the  other  this 
treatment  closed  the  ring  and  gave  2-amino-5-methyl-6-oxy- 
pyrimidine.  The  explanation  given  for  the  existence  of  these 
two  acids  was  that  they  represented  the  cis  and  trans  modifica- 
tions. 

Such  an  explanation  might  also  account  for  the  fact  that — 
like  Mtiller's  pyrimidines — certain  uracil  derivatives  dissolve 
in  alkali  and  on  precipitating  with  acids  give  the  corresponding 
uramidoacrylic  acids,  while  others — such  as  our  3-methyl- 
uracil — are  precipitated  in  the  form  having  the  closed,  uracil 
ring. 

EXPERIMENTAL   PART. 

The  preparation  of  2-ethylmercapto-6-thiopyrimidine  from 
2-ethylmercapto-6-chlorpyrimidine1  has  been  described  by 
Wheeler  and  Liddle.2  In  the  present  work  instead  of  employ- 
ing two  and  a  half  times  the  calculated  quantity  of  potassium 
hydrosulphide  we  have  taken  four  times  the  calculated  amount. 
By  this  method  a  yield  of  over  90  per  cent  of  the  calculated 
quantity  of  2-ethylmercapto-6-thiopyrimidine  was  obtained. 
HN— CS 

6-Thiouracil,   OC      CH  .—When        2-ethylmercapto-6-thio- 

I        II 
HN— CH 

pyrimidine  is  treated  with  concentrated  hydrochloric  acid 
the  pale  yellow  color  of  the  compound  changes  to  a  bright 
yellow.  If  water  is  added  the  color  disappears  or  becomes 
much  lighter.  If  this  solution  is  boiled  too  long  the  material 
is  completely  desulphurized  and  uracil  is  obtained.  The 
following  procedure,  however,  gave  a  yield  of  over  90  per  cent 
of  the  calculated  amount  of  6-thiouracil:  Nine  and  six- tenths 
grams  of  2-ethylmercapto-6-thiopyrimidine  were  added  to  a 
mixture  of  50  cc.  of  concentrated  hydrochloric  acid  and  50  cc. 
of  water.  On  warming,  mercaptan  was  evolved  and  solution 
took  place,  then  6-thiouracil  separated.  The  acid  was  evapo- 
rated on  the  steam  bath  and  the  residue  was  crystallized  from 
water. 

1  Wheeler  and  Johnson:  THIS  JOURNAL,  29,496  (1903) ;  31,  596  (1904). 

2  Ibid.,  40,  555  (1908). 


34  Wheeler  and  Johnson. 

N==CSCH3 

I          I 
2-Oxy-6-methylmercaptopyrimidine,    OC       CH       .  —  One  and 

HN  --  CH 

one-  tenth  grams  of  sodium  were  dissolved  in  25  cc.  of  methyl 
alcohol  and  6.1  grams  of  6-thiouracil  were  added.  The  mixture 
became  semisolid  owing  to  the  separation  of  a  colorless,  diffi- 
cultly soluble  sodium  salt.  Ten  grams  of  methyl  iodide  and 
25  cc.  more  methyl  alcohol  were  added.  On  warming  the 
mixture,  solution  soon  took  place  and  it  then  gave  a  neutral 
reaction.  The  alcohol  was  evaporated  and  the  residue  was 
treated  with  water.  Crystalline  material  separated  which, 
after  washing  with  water  and  drying,  weighed  5  grams,  or  73.7 
per  cent  of  the  calculated.  This  dissolved  easily  in  hot  water 
and  on  cooling,  long,  slender  needles  or  prisms  were  obtained 
melting  to  an  oil  with  no  effervescence  at  205°. 

Calculated  for 
C5H6ON2S.  Found. 

N  I9-71  I9-5° 


2-Oxy-3-methyl-6-methylmercaptopyrimidine,       OC        CH 

CH3N  -  CH 

—  Four  and  four-  tenths  grams  of  sodium  were  dissolved  in  100 
cc.  of  absolute  alcohol  and  then  10.5  grams  of  6-thiouracil 
were  added.  On  warming  a  clear  solution  resulted.  The 
solution  was  then  cooled  and  28  grams  of  methyl  iodide  were 
added.  A  mass  of  colorless  crystals  consisting  of  the  sodium 
salt  of  2-oxy-6-methylmercaptopyrimidine  separated.  On  add- 
ing 100  cc.  more  of  alcohol  and  warming  for  a  few  hours  a  clear 
solution  that  had  a  neutral  reaction  was  again  obtained.  The 
alcohol  was  then  evaporated  off,  the  final  portions  in  a  vacuum. 
The  product  was  separated  from  sodium  iodide  by  repeated 
extractions  with  chloroform.  When  about  9.5  grams  of  ma- 
terial had  been  extracted  it  was  purified  by  crystallizing  from 
benzene.  It  separated  in  needles  which  melted  at  124°  to 
a  clear  oil  without  effervescence. 


Researches  on  Pyrimidines.  35 

It  was  very  soluble  in  cold  water,  alcohol,  chloroform,  and 
boiling  ethyl  acetate. 

Calculated  for 

C6H8ON2S.  Found. 

17.95  I7-76 


When  the  above  mercapto- 

CH3N  --  CH 

pyrimidine  was  boiled  with  strong  hydrochloric  acid  mercaptan 
was  readily  given  off  and  on  evaporating  the  acid  under  di- 
minished pressure  colorless  prisms  were  obtained.  The  crude 
product  melted  at  22^-226°  while  i-methyl  uracil  melts  at 

i74°-i75°.1 

The  material  was  very  soluble  in  water  and  boiling  alcohol. 
It  crystallized  from  absolute  alcohol  in  rectangular  prisms 
and  from  hot  saturated,  aqueous  solutions  in  needles  which 
melted  at  232°  to  an  oil  without  effervescence.  It  gave  no 
red  color  with  diazobenzenesulphonic  acid  in  presence  of 
sodium  hydroxide.  With  bromine  water  and  barium  hy- 
droxide it  gave  a  purple  precipitate.  3-Methyluracil  is  less 
soluble  in  cold  water  than  i-methyluracil. 

Calculated  for 

Found. 


N  22.22  21.90 

Some  of  the  above  material  was  dissolved  in  cold  dilute 
sodium  hydroxide  and  the  solution  carefully  neutralized  with 
dilute  hydrochloric  acid.  The  pyrimidine  was  recovered 
unaltered  and  melted  at  232°. 

2-Oxy-3-benzyl-6-methylmercaptopyrimidine, 
N=CSCH3 

I  I 

OC        CH      .  —  Two  grams  of  2-oxy-6-methylmercapto- 

C6H5CH?N  --  CH 

pyrimidine  and  1.8  grams  of  benzyl  chloride  were  dissolved 
in  about  30  cc.  of  alcohol  containing  one  molecular  proportion 
of  potassium  hydroxide  (0.8  gram).  There  was  an  immediate 

1  Johnson  and  Heyl:  THIS  JOURNAL;  37,  633  (1907). 


36  Wheeler  and  Johnson. 

reaction  when  the  mixture  was  heated  and  potassium  chloride 
separated.  The  solution  was  warmed  on  the  steam  bath 
until  it  gave  no  alkaline  reaction.  The  potassium  chloride 
was  then  filtered  off  and  the  solution  was  cooled,  whereupon 
the  benzyl  derivative  separated  in  prisms  melting  at  148°- 
149°  to  an  oil  without  effervescence.  This  melting  point  was 
not  raised  by  recrystallizing  from  alcohol.  The  alcohol  filtrates 
were  evaporated  to  dryness  on  the  steam  bath  and  the  residue 
was  treated  with  dilute  sodium  hydroxide  to  remove  any  un- 
altered material.  The  insoluble  portion  melted  without 
further  purification  at  i46°-i48°  and  was  practically  pure 
3-benzyl  derivative.  The  yield  of  this  pyrimidine  was  2.9 
grams,  or  90  per  cent  of  the  calculated.  No  evidence  of  the 
formation  of  an  isomeric  benzyl  derivative  was  obtained. 

Ca  Iculated  for 
C12H12ON,S.  Found. 

N  12. 06  12.19 

When  this  mercaptobenzylpyrimidine  was  boiled  with 
hydrochloric  acid  it  gave  a  quantitative  yield  of  3-benzyl- 
uracil1  melting  at  i72°-i73°.  A  mixture  of  this  compound 
and  a  sample  of  3-benzyluracil  melted  at  i72°-i73°,  while 
a  mixture  of  the  pyrimidine  in  question  and  i-benzyluracil 
(m.  p.  175°)  melted  at  i4O°-i45°. 

Action  of  Methyl  Iodide  on  2-Ethylmercapto-6-oxy pyrimidine. 
— We  have  reexamined  the  action  of  methyl  iodide  on  the 
potassium  salt  of  2-ethylmercaptp-6-oxypyrimidine2  and  we 
now  find  that  both  i-  and  3-methyl  derivatives  are  formed. 
In  the  previous  work  only  the  i -methyl  derivative  was  iso- 
lated. A  mixture  of  2-ethylmercapto-6-oxypyrimidine  (15.2 
grams),  potassium  hydroxide  (5.6  grams),  and  methyl  iodide 
(18  grams),  in  75  cc.  of  alcohol  was  warmed  on  the  steam  bath 
until  the  solution  gave  a  neutral  reaction.  It  was  then  evap- 
orated to  a  syrup  and  a  little  water  was  added.  This  caused 
the  separation  of  3.6  grams  of  i-methyl-2-ethylmercapto-6- 
oxypyrimidine  which  was  filtered  off.  The  filtrate  was  boiled 
with  hydrochloric  acid  and  evaporated  to  dryness  and  the 

1  Johnson  and  Derby:  THIS  JOURNAL,  40,  444  (1908). 

2  Johnson  and  Heyl:  Loc.  cit. 


Researches  on  Pyrimidines.  37 

residue  was  repeatedly  extracted  with  boiling  alcohol.  The 
part  insoluble  in  alcohol  proved  to  be  uracil.  The  alcoholic 
solution  was  decolorized  with  animal  charcoal  and  some 
sulphur  dioxide.  The  alcohol  was  evaporated  and  the  residue 
was  fractionally  crystallized  from  water.  We  then  obtained 
the  3-methyluracil  melting  at  232°  and  the  i-methyl  deriva- 
tive melting  at  174°.  Owing  to  their  similar  solubility  in 
alcohol,  water,  and  other  solvents  it  is  impossible  to  make 
even  an  approximately  quantitative  separation  by  this  treat- 
ment. It  seems  to  us,  however,  that  the  i -methyl  derivative 
is  formed  in  largest  quantity.  Further  work  may  show  that 
these  proportions  vary  with  change  of  conditions. 

NEW  HAVEN,  CONN., 
April,  1909. 


[Reprinted  from  The  American  Chemical  Journal 
Vol.  XLII.    No.  2.    August,  1909.] 


[Contributions  from  the  Sheffield  Laboratory  of  Yale  University.] 

CLXVIIL— RESEARCHES  ON  PYRIMIDINES: 

THE   PREPARATION   OF    i,4-DIMETHYLURACIL   AND 

OF  THE  MONOBENZYL  DERIVATIVES  OF 

4-METHYLUR  ACIL.  * 

[FORTY-FOURTH  PAPER.] 

BY  HENRY  L.  WHEELER  AND  DAVID  F.  MCFARLAND. 

Behrend2  has  shown,  in  his  work  on  the  methylation  of 
4-methyluracil  with  alkali  and  methyl  iodide,  that  the  three 
products  i ,4-dimethyluracil,  3,4-dimethyluracil,  and  i,3,4-tri- 
methyluracil,  are  all  formed  and  have  to  be  dealt  with  in  addi- 
tion to  unaltered  material. 

List3  found  that  2-thio-4-methyluracil  (I.)  is  readily  methyl- 
ated and  that  the  alkyl  group  unites  with  the  sulphur, 
producing  2-methylmercapto-4-methyl-6-oxypyrimidine  (II.). 
List  did  not  determine  what  was  formed  on  further  alkyla- 
tion. 

1  Part  of  a  Thesis  presented  by  David  F.  McFarland  for  the  Degree  of  Ph.D., 
Yale,  1909. 

2  Behrend  and  Dietrich:  Ann.  Chem.    (Liebig),   309,  265    (1899).     Behrend  and 
Meyer:  Ber.  d.  chem.  Ges.,  33,  624  (1900).     Behrend  andThurn:  Ann.  Chem.  (Liebig), 
323,  160  (1902). 

3  Ann.  Chem.  (Liebig),  236,  12  (1886). 


IO2  Wheeler  and  McFarland. 

In  previous  papers  from  this  laboratory  it  has  been  shown 
that  2-mercapto-6-oxypyrimidines  usually  give  a  mixture 
of  the  i-  and  3-alkyl  derivatives  on  further  alkylation.1 

We  will  now  show  that  the  potassium  salt  of  List's  2-methyl- 
mercapto-4-methyl-6-oxypyrimidine,  in  alcoholic  solution,  al- 
kylates  almost  entirely  in  the  i -position  with  methyl  iodide 
and  that  i,4-dimethyl-2-methylmercapto-6-oxypyrimidine  (III.) 
is  formed.  There  are  indications  also,  in  this  reaction,  of 
the  formation  of  2-methylmercapto-4-methyl-6-methoxypyr- 
imidine  in  small  amount. 

Since  the  alkylmercaptopyrimidines  easily  evolve  mercaptan 
and  form  the  corresponding  uracil  derivatives  on  boiling 
with  hydrochloric  acid,  this  method  is  the  best  (Darstellung) 
for  the  preparation  of  i  ,4-dimethyluracil  (IV.). 

By  condensing  acetoacetic  ethyl  ester  with  thiourea  in 
alcoholic  solution  and  in  the  presence  of  two  molecular  pro- 
portions of  sodium  ethylate,  a  quantitative  yield  of  List's 
2-thio-4-methyluracil  (I.)  may  be  obtained.  The  condensa- 
tion also  takes  place  in  alkaline  aqueous  solution  but  the 
yield  is  not  as  good.  Even  this  process  is  far  superior  to  the 
original  methods.2 

The  steps  in  the  synthesis  of  i,4-dimethyluracil  may  be 
represented  as  follows : 

HN CO 

I  I 

SC         CH     — >• 

I  II 

HN CCH3 

CH3N CO 

I  I 

OC         CH 


Acetoacetic  ethyl  ester  condenses  with  ethylpseudothiourea, 

1  For  a  list  of  these  cases  see  our  forty-third  paper  on  pyrimidines,  THIS  JOURNAL, 
42,  (1909). 

2  Nencki  and  Sieber:  J.  prakt.  Chem.,  [2]  25,  72  (1882).     List:  Loc.  tit. 


Researches  on  Pyrimidines.  103 

H2N  —  C(SC2H5)NH,  in  alkaline  aqueous  solution  more 
smoothly  and  gives  a  larger  yield  (over  80  per  cent)  of  mer- 
captopyrimidine  than  in  the  case  of  the  corresponding  con- 
densations of  the  sodium  salts  of  either  ethyl  formylacetate 
or  ethyl  formylpropionate. 

When  2-ethylmercapto-4-methyl-6-oxypyrimidine  (V.),  pre- 
pared in  this  manner,  was  treated  with  sodium  hydroxide  and 
benzyl  chloride,  a  mixture  of  i-benzyl-2-ethylmercapto- 
4-methyl-6-oxypyrimidine  (VI.)  and  2-ethylmercapto-4-methyl- 
6-benzyloxypyrimidine  (VII.)  was  obtained.  This  mixture, 
which  was  obtained  as  an  oil  insoluble  in  alkali,  could  not 
be  separated  by  distillation  under  reduced  pressure.  When 
it  was  boiled  with  hydrochloric  acid  mercaptan  escaped  and 
a  new  benzyl-4-methyluracil,  melting  at  194°,  along  with 
4-methyluracil,  was  obtained. 

CCH5CH2N CO  HN CO  N=COCH2C6H6 

*—  C2H5SC       CH  — -3 


FX1IN V^V^Xlj  CH3N 

VIII.  IX. 

Hagen1  described  a  benzyl-4-methyluracil  melting  at  233° 
which  he  obtained  in  very  small  amount — the  quantity  being 
only  sufficient  for  analysis — by  heating  the  dry  potassium 
salt  of  4-methyluracil  at  a  high  temperature  with  benzyl 
chloride.  This  substance  is  given  in  Beilstein's  Handbuch? 
as  i -benzyl-4-methyluracil  (VIII.). 

We  now  find  that  this  is  incorrect  and  that  the  compound 
is  3-benzyl- 4-methyluracil  (XIII.).  The  proof  of  the  struc- 
ture of  these  compounds  was  obtained  as  follows:  1,4- Dime thyl- 

1  Ann.  Chem.  (Liebig),  244,  9  (1888). 

2  [3]  2,  529. 


IO4  Wheeler  and  McFarland. 

uracil  (XI.)  was  treated  with  potassium  hydroxide  and  benzyl 
chloride  in  alcoholic  solution.  This  gave  i  ,4-dimethyl-3-benzyl- 
uracil  (XII.),  melting  at  85°-86°.  Hagen's  benzylmethyl- 
uracil,  which  we  find  is  easily  obtained,  along  with  the  isomer 
melting  at  194°,  when  4-methyluracil,  potassium  hydroxide 
and  benzyl  chloride  are  warmed  in  alcoholic  solution,  was 
then  methylated;  the  same  dimethylbenzyluracil  melting 
at  85°-86°  was  thereby  obtained. 

CH,N CO  CH3N CO  HN CO 

II  II 

OC         CH  «<—  OC         CH 

I  II  I  II 

C6H5CH2N CCH3       C6H5CH2N CCH3 

XII.  XIII. 

When  the  new  i-benzyl-4-methyluracil  (VIII.)  was  methyl- 
ated it  gave  the  isomeric  i-benzyl-3,4-dimethyluracil  (IX.), 
melting  at  164°. 

The  possibility  of  an  alkylation  taking  place  in  the  5 -position 
in  the  case  of  pyrimidines  derived  from  acetoacetic  ester 
had  to  be  considered,  at  this  point,  before  the  above  results 
could  be  taken  as  proof  of  the  structures  assigned  to  the  benzyl 
compounds  in  question.  Barbituric  acid  or  2,4,6-trioxy- 
pyrimidine  alkylates  under  the  same  conditions  in  the  5-posi- 
tion.1 

From  the  analogy  which  exists  between  acetoacetic  ester 
and  malonic  ester  it  might  be  expected  that  4-methyluracil 
or  2-ethylmercapto-4-methyl-6-oxypyrimidine  might  react  in 
the  tautomeric  forms  represented  by  formulas  (XIV.)  and 
(XV.)  and  yield  5 -benzyl  derivatives. 

N CO  N CO 

II  I  II  I 

HOC         CH2  C2H5SC         CH2 

II  II 

N^=<:CH3  N=CCH3 

XIV.  XV. 

In  order  to  prepare  4-methyl-5-benzyluracil  (XVIII.) 
it  was  necessary  to  condense  benzylacetoacetic  ester  with  a  urea 

1  Conrad  and  Gutzeit:  Ber.  d.  chem.  Ges.,  14, 1643  (1881) ;  15,  2846  (1882).    Fischer 
and  Dilthey:  Ann.  Chem.  (Liebig),  333,  338  (1904). 


Researches  on  Pyrimidines.  105 

derivative.  This  ester  proved  to  be  one  of  those  /?-ketone 
esters  which  failed  to  condense  satisfactorily  by  the  general 
method  with  the  pseudothioureas  in  aqueous  solution.  We 
find,  however,  that  it  condenses  in  alcoholic  solution  with 
thiourea  in  the  presence  of  sodium  ethylate,  giving  the  sodium 
salt  of  2-thio-4-methyl-5-benzyluracil  (XVI.).  In  order 
to  desulphurize  this  it  was  found  best  to  convert  it  into  2-ethyl 
mercapto-4-methyl-5-benzyl-6-oxypyrimidine  (XVII.)  which, 
en  boiling  with  hydrochloric  acid,  easily  gave  the  desired 
4-methyl-5-benzyluracil  (XVIII.)  melting  at  249°-25o°. 

HN CO         »  HN CO  HN — 

II  ->          I  I  — *    I 

SC         CCH2C6H5  C2H5SC         CCH2C6H5      OC 


HN CCH3  N CCH3  HN 

XVI.  XVII.  XVIII. 

Since  this  compound,  melting  at  249°-25O°,  is  different 
from  either  of  the  above  benzylmethyluracils  it  follows  that 
in  the  alkylation  of  the  pyrimidines  derived  from  acetoacetic 
ester,  under  the  conditions  stated,  the  benzyl  group  does  not 
enter  the  5-position,  and  that  the  various  benzyl  compounds 
are  correctly  represented  by  the  formulas  given  above.  The 
isomeric  benzyloxypyrimidines  would  not  be  stable  when 
boiled  with  hydrochloric  acid  and  are  therefore  excluded. 
This  otherwise  completes  the  list  and  settles  the  structure 
of  the  monobenzyl  derivatives  of  4-methyluracil. 

EXPERIMENTAL   PART. 

i,4-Dimethyl-2-methyimercapto-6-oocypyrimidine, 
CH3N CO 

CH3SC         CH. — An    almost    quantitative   yield  of  2-thio-4- 

N CCH3 

methyluracil  was  usually  obtained  when  30  grams  of  aceto- 
acetic ester  and  two  molecular  quantities  of  sodium  ethylate, 
made  by  dissolving  10.6  grams  of  sodium  in  200  cc.  of  absolute 
alcohol,  were  warmed  for  half  an  hour  with  17.5  grams  of  thio- 


io6  Wheeler  and  McFarland. 

urea.  On  evaporating  the  alcohol  on  the  steam  bath,  which  ap- 
pears to  render  the  condensation  more  nearly  complete,  the 
sodium  salt  of  2-thio-4-methyluracil  remained.  This  salt  easily 
dissolved  in  water.  On  addition  of  acetic  acid  to  the  solu- 
tion, 2-thio-4-methyluracil  was  precipitated.  The  precipi- 
tate is  apt  to  carry  down  with  it  some  of  the  sodium  salt, 
and  it  was  found  advisable  to  warm  it,  after  filtering,  with 
water  acidified  with  acetic  acid.  Then  on  washing  with  water 
it  is  obtained  pure  and  free  from  sodium. 

When  2-thio-4-methyluracil  is  treated  with  two  molecular 
proportions  of  potassium  hydroxide  and  methyl  iodide  a 
considerable  quantity  of  2-methylmercapto-4-methyl-6-oxy- 
pyrimidine  is  obtained.  In  order  to  produce  a  satisfactory 
alkylation  on  the  nitrogen  it  is  necessary  to  use  a  greater 
excess  of  alkali  and  methyl  iodide.  Potassium  hydroxide 
gives  better  results  in  nitrogen  alkylation  than  sodium  hydr- 
oxide. 

Thirty  grams  of  2-thio-4-methyl-6-oxypyrimidine  were 
dissolved  with  35  grams  of  potassium  hydroxide  in  150  cc. 
of  absolute  alcohol.  The  potassium  salt  formed  was  much 
more  soluble  than  the  free  pyrimidine.  After  cooling  the 
solution,  94  grams  of  methyl  iodide,  an  excess  of  4  grams 
over  that  calculated  for  3  molecular  quantities,  were  gradually 
added  and  the  mixture  was  allowed  to  stand  two  days.  At 
the  end  of  that  time,  about  6  hours'  gentle  heating  on  the  steam 
bath  was  required  to  complete  the  reaction  so  that  the  solu- 
tion gave  no  alkaline  test  with  moist  turmeric  paper.  The 
alcohol  was  then  evaporated,  under  diminished  pressure, 
and  the  solid  residue  was  treated  with  dilute  sodium  hydrox- 
ide. The  undissolved  portion  was  filtered  and  washed  with 
a  little  water.  Twenty-five  and  one- tenth  grams  of  i,4-di- 
methyl-2-methylmercapto-6-oxypyrimidine  melting  at  8  5°-9O° 
were  obtained.  An  additional  2.3  grams  were  recovered 
by  shaking  the  alkaline  mother  liquor  with  ether,  making  the 
total  yield  of  the  compound  27.4  grams,  or  76.4  per  cent,  of 
the  calculated  yield.  From  the  alkaline  solution  4.5  grams 
of  2-methylmercapto-4-methyl-6-oxypyrimidine,  formed  by 
incomplete  methylation,  were  obtained  on  acidifying.  Al- 


Researches  on  Pyrimidines.  107 

lowing  for  this,  the  yield  of  i,4-dimethyl-2-methylmercapto- 
6-oxypyrimidine  becomes  91.2  per  cent  of  the  calculated. 

In  another  experiment  where  only  two  molecular  propor- 
tions of  alkali  and  of  methyl  iodide  were  used  with  27  grams 
of  2-thio-4-methyluracil,  the  amount  of  intermediate  2-methyl- 
mercapto-4-methyl-6-oxypyrimidine  was  largely  increased,  8 
grams  of  it  being  formed,  with  a  corresponding  decrease  of 
dimethylmercapto  compound.  This  shows  that  a  large 
excess  of  alkali  and  of  methyl  iodide  is  necessary  in  order 
to  completely  methylate  2-thiouracil. 

A  small  quantity  of  oily  substance,  with  a  pungent  odor 
resembling  that  of  parsnips,  coated  the  material  insoluble 
in  alkali.  It  is  probable  that  this  oil  is  a  6-methoxy  derivative 
but  not  enough  was  obtained  to  permit  of  its  identification. 
When  the  material  insoluble  in  alkali  was  crystallized  from 
water  it  gave  needles  which  melted  sharply  at  94°  and  the 
results  on  analysis  agreed  with  those  calculated  for  i,4-dimethyl- 
2  -  me  thy  Imercap  to-6-oxy  py  rimidine . 

Calculated  for 
C7H10ON2S.  Found. 

N  16.22  16.47 

The  substance  is  readily  soluble  in  alcohol  and  boiling 
water,  crystallizing  from  aqueous  solutions  in  silky  needles. 
It  is  extremely  soluble  in  ether,  chloroform  and  benzene, 
and  rather  difficultly  soluble  in  petroleum  ether.  It  sublimes 
readily  at  the  temperature  of  the  steam  bath,  condensing 
again  in  fine  silky  needles.  It  is  easily  volatile  with  steam, 
and  solutions  containing  it  cannot  be  evaporated  on  the  steam 
bath  without  loss. 

Action  of  Hydrochloric  Acid:  i,4-Dimethyluracil. — The  above 
i, 4-dimethyl-2-me  thy  Imercap  topyrimidine  was  boiled  for  one 
hour  with  strong  hydrochloric  acid  under  a  reflux  condenser 
to  prevent  loss  of  the  volatile  compound.  By  this  treatment 
it  was  quantitatively  converted  into  Behrend's  /?-dimethyl- 
uracil  ( 1,4- dime thyluracil).  One  recrystallization  from  hot 
water  gave  material  melting  sharply  to  a  clear  oil  at  260 °- 
261°. 


io8  Wheeler  and  McFarland. 

No  trace  of  Behrend's  isomeric  «-dimethyluracil  (3,4-di- 
methyluracil)  melting  at  220°  was  found  in  any  of  the  mother 
liquors  from  the  above.  It  is  reasonably  certain,  therefore, 
that  the  corresponding  2-methylmercapto-3,4-dimethyl-6-oxy- 
pyrimidine  was  not  formed  in  appreciable  quantities. 

i-Benzyl-2-ethylmercapto-4-methyl-6-oxypyrimidine, 
CCH5CH2N CO 

C2H5SC          CH.  —  2-Ethylmercapto-4-methyl-6-oxypyrimi- 

N CCH3 

dine  was  prepared  by  condensing  acetoacetic  ethyl  ester  with 
ethyl  pseudothiourea  in  aqueous,  alkaline  solution;  from  54.5 
grams  of  acetoacetic  ester  a  yield  of  58.5  grams  of  crude  mer- 
capto  compound  was  obtained,  or  81.5  per  cent  of  the  calcu- 
lated. 

Twenty  grams  of  this  compound  were  added  to  a  solution 
of  2.95  grams  of  sodium  in  60  cc.  of  alcohol.  After  complete 
solution  had  been  effected  16.2  grams  of  benzyl  chloride  were 
added  and  the  mixture  was  heated  on  the  water  bath  until 
no  further  alkaline  reaction  could  be  obtained  with  moist 
turmeric  paper.  This  required  about  four  hours.  The  alcohol 
was  then  evaporated  under  diminished  pressure  and  the 
residue  treated  with  20  cc.  of  water  and  10  cc.  of  dilute  sodium 
hydroxide.  A  heavy  oil  remained  undissolved.  This  was 
shaken  out  with  ether;  the  ether  solution  was  washed  with 
water  to  remove  alcohol,  dried  over  solid  potassium  hydroxide, 
and  filtered  into  a  weighed  flask.  After  evaporating  the 
ether,  20.7  grams  of  oil  remained,  or  68  per  cent  of  the  calcu- 
lated monobenzyl  derivative.  From  the  above  alkaline 
solution  9  grams  of  unaltered  substances  and  from  the  oil  6  grams 
of  low-boiling  material  were  obtained.  Allowing  for  these 
weights,  the  yield  of  monobenzyl  derivative  is  87.5  per  cent. 

The  oil  was  distilled  at  22  mm.  pressure  and  after  about 
six  grams  of  low-boiling  oil  (benzyl  chloride?)  had  distilled 
over,  the  temperature  rose  to  224°  and  a  little  over  10  grams 
of  material  distilled  between  this  and  236°.  The  greater 
part  boiled  near  227°.  The  temperature  rose  slowly,  toward 


Researches  on  Pyrimidines.  109 

the  last  to  260°,  where  the  distillation  was  stopped.  The 
fractions  obtained  were  only  slightly  colored.  None  of  them 
gave  any  solid  even  when  cooled  to  — 15°.  Analyses  were 
made  of  two  separate  fractions,  one  (A)  boiling  at  227°-228°, 
and  the  other  (B)  at  228°-26o°.  Both  gave  excellent  re- 
sults for  a  monobenzyl  derivative  of  2-ethylmercapto-4-methyl- 
6-oxypyrimidine. 

Calculated  for  Found. 

CuHi6ON2S.  A.  B. 

N  10.77  10.63  10.62 

Action  of  Hydrochloric  Acid:  i- Benzyl- 4-methyluracil. — Two 
grams  of  the  above  fraction  B  were  boiled  for  two  hours  with 
15  cc.  of  concentrated  hydrochloric  acid,  during  which  time 
mercaptan  was  evolved.  The  solution  was  evaporated  to 
dry  ness,  a  solid  residue  weighing  1.3  grams,  which  nearly 
all  dissolved  in  boiling  water  remaining.  After  filtering  off  the 
small  amount  of  gummy  residue  which  did  not  dissolve,  a 
crystalline  mass  separated  on  cooling.  It  dissolved  in  boiling 
alcohol,  and,  on  cooling  gave  colorless,  rounded,  lozenge- 
shaped  crystals  melting  to  a  clear  oil  at  194°.  Analysis 
showed  this  to  be  a  monobenzyl-4-methyluracil. 

Calculated  for 
C12H]2O2No.  Found. 

N  12.96  12.93 

The  compound  dissolves  easily  in  cold  chloroform,  moder- 
ately in  hot  alcohol,  and  rather  difficultly  in  hot  water.  The 
crystals  from  alcohol  are  characteristic. 

By  evaporation  of  the  aqueous  mother  liquor  from  the  above 
compound,  material  was  obtained  which  crystallized  in  clus- 
ters of  fine  needles.  It  had  no  sharp  melting  point  but  decom- 
posed at  270°-30O°.  Analyses  of  this  material  gave  results 
which  agreed  with  those  calculated  for  4-methyluracil.  When 
it  was  mixed  with  pure  4-methyluracil,  the  decomposition 
point  was  not  lowered.  From  the  two  grams  of  oil  hydrolyzed 
there  were  obtained  about  0.3  gram  of  i-benzyl-4-methyl- 
uracil  and  0.6  gram  of  4-methyluracil.  This  result  indicates 
that  the  fraction  of  oil  boiling  at  228°-26o°  consisted  about 


no  Wheeler  and  McFarland. 

one- third  of  i-benzyl-2-ethylmercapto-4-methyl-6-oxypyrim- 
idine  and  two-thirds  of  the  isomeric  2-ethylmercapto-4-methyl- 
6-benzyloxypyrimidine. 

A  similar  hydrolysis  of  fraction  A  of  the  oil  yielded  approx- 
imately equal  proportions  of  4-methyluracil  and  i-benzyl- 
4-methyluracil,  so  that  this  fraction  consisted  of  a  corre- 
sponding mixture  of  the  mercaptobenzyl  compounds.  Re- 
peated fractional  crystallization  of  all  the  residues  from  this 
experiment  failed  to  give  any  other  substance  besides  the  two 
described.  No  trace  of  the  monobenzyl-4-methyluracil 
described  by  Hagen1  was  found,  although  a  painstaking  search 
was  made  for  it. 

Action  of  Benzyl  Chloride  upon  4-Methyluracil:  j-Benzyl- 
4-methyluracil. — The  4-methyluracil  for  this  experiment  was 
made  by  boiling  2-ethylmercapto-4-methyl-6-oxypyrimidine 
with  strong  hydrochloric  acid  until  mercaptan  ceased  to  be 
evolved.  It  was  purified  by  crystallization  from  water. 

Five  and  a  half  grams  of  4-methyluracil  were  heated  with 
2.44  grams  of  potassium  hydroxide  in  50  cc.  of  absolute  alcohol. 
Complete  solution  did  not  take  place  until  a  further  addition 
of  50  cc.  of  alcohol  and  28  cc.  of  water  had  been  made.  Six 
grams  of  benzyl  chloride,  or  one-half  gram  excess  over  the 
calculated,  was  then  added  and  the  mixture  heated  for  three 
hours  on  the  steam  bath  or  until  no  alkaline  reaction  was  ob- 
tained. 

On  evaporating  the  alcohol,  a  partially  solidified  mass 
remained.  Part  of  this  dissolved  when  warmed  with  dilute 
sodium  hydroxide.  The  insoluble  part  formed  a  resinous 
semisolid  on  cooling;  this  gum  could  not  be  induced  to  crys- 
tallize. 

From  the  alkaline  solution  acetic  acid  precipitated  a  mix- 
ture. This  was  boiled  with  about  50  cc.  of  alcohol.  The 
portion  which  did  not  dissolve  proved  to  be  chiefly  4-methyl- 
uracil. On  cooling  the  alcoholic  solution,  pearly,  irridescent,, 
diamond-shaped  plates  separated  which  melted  about  220°— 
235°,  at  least  30°  higher  than  i-benzyl-4-methyluracil.  Three 
crystallizations  from  alcohol  raised  the  melting  point  to  233°- 

1  Loc.  cil. 


Researches  on  Pyrimidines.  1  1  1 

235°.  It  therefore  agreed  with  that  given  by  Hagen  for  his 
benzyl-4-methyluracil.  The  compound  is  very  difficultly 
soluble  in  hot  alcohol  and  still  more  difficultly  in  boiling  water. 
It  is  almost  insoluble  in  cold  chloroform.  An  analysis  of  the 
substance  melting  at  233°-235°  gave  results  agreeing  with 
those  calculated  for  monobenzyl-4-methyluracil. 

Calculated  for 

Found. 


N  12.96  13.18 

The  alcoholic  mother  liquors  from  this  were  evaporated  to 
dryness.  The  remaining  material  was  then  shaken  with 
chloroform.  The  insoluble  part  proved  to  be  almost  pure 
3-benzyl-4-methyluracil  (Hagen's  compound).  The  chloro- 
form solution  was  evaporated  to  dryness  and  the  residue 
was  crystallized  from  alcohol,  whereupon  the  isomeric  i  -benzyl- 
4-methyluracil  was  obtained. 

A  second  benzylation  of  4-methyluracil,  with  7  grams  of 
the  pyrimidine  and  two  molecular  proportions  of  potassium 
hydroxide  (6.22  grams)  and  of  benzyl  chloride  (14.5  grams) 
in  115  cc.  of  alcohol  and  35  cc.  of  water,  gave  3.6  grams  of 
gum,  insoluble  in  alkali,  2  grams  of  unaltered  4-methyluracil, 
and  about  2  grams  each  of  the  isomeric  nitrogen  benzyl- 
4-methyluracils. 

CH3N  -  CO 

I  I 

i  ,4-Dimethyl-3-benzyluracil,  OC         CH  .  —  Hagen's 

C6H5CH2N  --  CCH3 

benzyl-4-methyluracil  melting  at  233°  (1.6  grams)  was  dis- 
solved in  90  cc.  of  methyl  alcohol  with  three  molecular  propor- 
tions of  potassium  hydroxide  and  warmed  for  three  hours 
and  a  half  with  methyl  iodide  (3.25  grams).  The  alcohol 
was  then  evaporated  and  the  residue  was  stirred  with  dilute 
sodium  hydroxide.  This  left  1.8  grams  of  oil  which  on  cooling 
solidified.  It  was  dissolved  in  ether  and  the  clear,  filtered 
solution  was  allowed  to  evaporate  slowly  in  a  tall  test  tube. 
Beautiful,  clear,  transparent,  prismatic  tables  were  then 
obtained  which  melted  sharply  at  85°-86°.  When  these 


H2  Wheeler  and  McFarland. 

were  mixed  with  i  ,4-dimethyl-3-benzyluracil  prepared  by 
benzylating  i,4-dimethyluracil  the  melting  point  was  not 
lowered.  The  two  preparations  agreed  in  all  respects  and  are 
identical. 

The  preparation  of  this  compound  from  i  ,4-dimethyluracil 
was  as  follows:  Two  and  eighty-five  hundred ths  grams  of 
i,4-dimethyluracil  and  one  molecular  quantity  of  potassium 
hydroxide  were  dissolved  in  120  cc.  of  95  per  cent  alcohol. 
One  molecular  portion  of  benzyl  chloride  was  added  and  the 
mixture  was  heated  on  the  steam  bath  until  a  neutral  reac- 
tion was  obtained.  A  considerable  amount  of  potassium 
chloride  which  separated  was  filtered  off  and  the  alcohol 
was  evaporated,  a  partially  solid  mass  remaining.  A  portion 
of  this  dissolved  when  treated  with  sodium  hydroxide,  leaving 
2.1  grams  of  oil,  which  finally  solidified.  When  crystallized 
from  ether  as  described  above  it  melted  sharply  at  85°-86° 
and  the  analytical  results  were  as  follows: 

Calculated  for  Found. 

C18H1402N2.  I.  II. 

N  12.17  12.41  12.22 

This  substance  was  found  to  be  extremely  soluble  in  alcohol 
and  benzene,  much  less  so  in  ether,  and  only  slightly  in  petro- 
leum ether. 

C6H5CH2N CO 

i-Benzyl-3,4-dimethyluracil,  OC          CH — This    com- 

I  II 

CH3N CCH3 

pound,  isorneric  with  the  above,  was  produced  when  1.45 
grams  of  i-benzyl-4-methyluracil  melting  at  194°  was  warmed 
for  about  four  hours  with  molecular  proportions  of  potassium 
hydroxide  and  methyl  iodide  in  50  cc.  of  95  per  cent  alcohol. 
The  potassium  iodide  which  separated  during  the  reaction 
was  filtered  off  and  the  alcohol  evaporated  to  dryness.  The 
residue  was  treated  with  dilute  sodium  hydroxide,  washed 
with  water,  and  dried.  It  weighed  1.2  grams,  or  76  per  cent 
of  the  calculated.  When  crystallized  from  alcohol,  beautiful, 


Researches  on  Pyrimidines.  113 

long,  colorless    prisms  melting  at  164°    to  a  clear  oil,  were 
obtained. 

An  analysis  gave  results  agreeing  with  the  calculated  for 
i-benzyl-3,4-dimethyl  uracil. 

Calculated  for  Found. 

C13HU02N2.  I.  II. 

N  12.17  12.43  12.32 

The  alkaline  solution  above    gave  i,4-dimethyluracil  when 
acidified  with  acetic  acid,  the  alkylation  not  being  complete. 

HN CO 


U,    SC 


2-Thio-4-melhyl-  j-benzyluracil,    SC          CCH2C6H5.  —  Benzvl- 

I  II 

HN  -  CCH3 

acetoacetic  ethyl  ester  was  prepared  by  the  action  of  benzyl  chlo- 
ride upon  the  sodium  salt  of  acetoacetic  ester,  according  to  the 
method  of  Bhrlich.1  The  portion  boiling  at  i94°-2O4°  at 
40  mm.  pressure  was  used  in  the  following  work,  part  of  which 
was  done  by  Mr.  McKay  S.  Howard  : 

Ten  grams  of  benzy  lace  toace  tic  ester  and  4  grams  of  thiourea 
were  added  to  a  solution  of  sodium  ethylate  made  by  dissolving 
three  grams  of  sodium  in  75  cc.  of  absolute  alcohol.  The  mix- 
ture was  heated  on  the  steam  bath  for  four  hours.  The  alco- 
hol was  then  evaporated  and  the  residue  was  dissolved  in 
water.  On  the  addition  of  dilute  acetic  acid  2-thio-4-methyl- 
5-benzyl-6-oxypyrimidine  was  precipitated.  The  yield  was 
7.4  grams,  or  70  per  cent  of  the  calculated.  The  substance 
was  very  difficultly  soluble  in  water  but  more  easily  in  alcohol, 
from  which  it  crystallized  in  colorless,  leafy  plates  or  scales. 
After  two  recrystallizations  it  melted  to  a  clear  oil  at  257°- 

258°. 

Calculated  for  Found. 

I.  II. 


N  12.07  12.12  12.13 

In  another  experiment,  20  grams  of  benzy  lace  toace  tic 
ester  gave  13.1  grams  of  the  condensation  product,  or  62.4 
per  cent  of  the  calculated. 

1  Ann.  Chem.  (Liebig),  187,  12  (1875). 


H4  Wheeler  and  McFarland. 

2-Ethylmercapto-4-methyl-  ^-benzyl-  6-oxypyrimidine, 
HN CO 

I  I 

C2H5SC         CCH2C6H5.— The  above  2-thiouracil  derivative  was 

I!        II 
N CCH3 

dissolved  in  alcohol  containing  one  molecular  proportion  of 
sodium  ethylate  and  then  allowed  to  digest  with  a  slight  excess 
of  ethyl  bromide  until  the  solution  was  neutral.  The  product, 
which  was  almost  insoluble  in  water,  and  soluble  only  with 
difficulty  in  cold  alcohol,  formed  fine,  prismatic  needles  melt- 
ing sharply  at  166°. 

Calculated  for  Found. 

CWH16ON2S.  I.  II. 

N  10.77  ii. oo  10.56 

HN CO 

4-M  ethyl- 5-benzyluracil,  OC         CCH2C8H5.— Two    grams   of 

HN CCH3 

the  above  mercapto  compound  were  allowed  to  digest  for  24 
hours  on  the  steam  bath  with  50  cc.  of  concentrated  hydro- 
chloric acid.  Mercaptan  escaped,  and,  on  cooling,  1.6  grams 
of  4-methyl-5-benzyluracil,  or  96  per  cent  of  the  calculated, 
separated.  The  substance  was  recrystallized  from  water 
and  alcohol.  It  gave  diamond- shaped  plates  melting  to  a 
clear  oil  at  249°-25o°. 

Calculated  for 
Ci2H12O2N2.  Found. 

N  12.96  13.06 

2  -  Benzylmercapto-4-methy  I-  5  -  benzyl- 6-oxypyrimidine. — This 
was  prepared  by  benzylating  2-thio-4-methyl-5-benzyluracil 
with  molecular  quantities  of  benzyl  chloride  and  sodium 
ethylate  in  alcoholic  solution.  It  is  nearly  insoluble  in  water. 
From  alcohol  it  separates  in  matted  masses  of  long,  colorless 
needles  and  it  melts  to  a  clear  oil  at  194°. 

Calculated  for  Found. 

CwHi8ON2S.  I.  II. 

N  8.69  8.58  8.75 


Researches  on  Pyrimidines.  115 

This  benzylmercapto  compound  proved  to  be  very  stable 
when  boiled  with  hydrochloric  acid.  It  was  not  desulphurized 
when  given  the  same  treatment  as  that  in  the  case  of  the  corre- 
sponding ethylmercapto  derivative.  When  boiled  with  hydro- 
bromic  acid  it  was  finally  desulphurized  and  4-methyl-5-benzyl- 
uracil  was  obtained.  In  view  of  this  behavior  it  is  therefore 
not  a  matter  of  indifference  what  mercapto  derivative  is  chosen 
for  these  desulphurizations. 

NEW  HAVEN,  CONN., 
May,  1909. 


[Reprinted  from  The  American  Chemical  Journal, 
Vol.  XLII.    No.  3.    September,  1909.] 


[Contributions  from  the  Sheffield  Laboratory  of  Yale  University.] 

CLXIX.—  RESEARCHES  ON  PYRIMIDINES: 

SULPHUR     DERIVATIVES     OF     5-HYDROXYURACIL: 

PREPARATION   OF   5-BENZYLMERCAPTOURACIL 

AND  5-BENZYLMERCAPTOCYTOSINE. 

[FORTY-FIFTH   PAPER.] 
BY  TREAT  B.  JOHNSON  AND  HERBERT  H.  GUEST. 

Several  investigators  have  shown  that  the  methylene  hydro- 
gens of  cyclic  compounds  which  contain  the  — S — CH2 — CO — 


272  Johnson  and  Guest. 

grouping — rhodanic  acids1  (I)  and  pseudothiohydantoins2 
(II)  and  (III) — react  with  aldehydes,  in  presence  of  alkali, 
giving  unsaturated  condensation  products  (IV).  It  has  also 

CH2— S  CH2— S  CH2— S 

CO     CS  CO     CO(NHR)  CO     CNR2 

\/  V  V 

NR  NR  N 

I.  II.  III. 

RCH:C S  HOOCCOCH— S 

I         I 
CO     C:NC8H5 


NH 
V. 

been  shown  that  the  methylene  group  of  arylpseudothiohydan- 
toins  is  capable  of  condensing  with  diethyl  oxalate  in  presence 
of  sodium  ethylate.  Wheeler  and  Jamison,3  for  example, 
prepared  in  this  manner  phenylpseudothiohydantoinglyoxylic 
acid  (V),  from  stable  phenylpseudothiohydantoin.  Loven4 
examined  the  behavior  of  the  methylene  groups  in  thiodigly- 
collic  acid  towards  benzaldehyde  and  obtained  the  sulphide 
of  a-mercaptocinnamic  acid,  (C6H5CH :  CCOOH)2S,  but  no 
attempts,  so  far  as  the  writer  is  aware,5  have  been  made  to 
condense  ethyl  formate  or  diethyl  oxalate  with  any  acyclic 
compound  containing  the  grouping  — S — CH2 — CO— . 

A  search  of  the  literature6  reveals  the  fact  that  no  a-  or 

1Nencki:  Ber.  d.  chem.  Ges.,  17,2278  (1884).  Giesberg  and  Bondzynski:  Ibid.. 
19,  113  (1886).  Bondzynski:  Monats.  Chem..  8,  349  (1887).  Zipser:  Ibid.,  23,  958; 
Centralb.,  1903,  I,  283.  Andreasch  and  Zipser:  Monats.  Chem.,  24,  499;  25,  159; 
26,  1191;  Chem.  Ztg.,  26,  54,  623.  Stuchetz:  Monats.  Chem.,  26,  1209.  Andreasch: 
Ibid.,  27,  1211.  Wagner:  Ibid.,  27,  1223.  Bargellini:  Atti.  Accad.  Lincei,  [5]  15, 
I,  35,  181;  Centralb.,  1906,  I,  1436,  1438;  Gazz.  Chim.  Ital.,  36,  II,  129. 

2  Andreasch:  Monats.  Chem.,  8,  407;  10,  73,  75;  Ber.  d.  chem.  Ges..  31,  138; 
Centralb.,  1899,  II,  804.     Wheeler  and  Jamieson:  J.  Am.  Chem.  Soc..  25,  366  (1903). 

3  Loc.  cit. 

4  Ber.  d.  chem.  Ges.,  18,  3243  (1885). 

5  The  writer  has  signified  in  a  previous  paper  (Tins  JOURNAL,  31,  290)  his  intention 
of  condensing  diethyl  oxalate  with  diethyl  thiodigly collate. 

8  Beilstein's  Handbuch,  Vol.  I. 


Researches  on  Pyrimidines.  273 

^-mercapto  derivatives  of  acrylic  acid  (VI),  corresponding 
to  a-hydroxy-  (VII),  /?-hydroxy-  (VIII),  and  a,/?-dihydroxy- 
acrylic  acids  (IX),  have  been  described. 

CH2:CHCOOH. 
VI. 

ft.  a.  f.  a. 

CH2  :  C(OH)COOH  CH2  :  C(SR)COOH. 

VII. 

HOCH  :  CHCOOH  RSCH  :  CHCOOH. 

VIII. 

HOCH  :  C(OH)COOH          RSCH  :  C(SR)COOH. 


RSCH  :  C(OH)COOH  HOCH  :  C(SR)COOH. 

X. 

It  was,  therefore,  of  especial  interest  to  determine  whether 
ethyl  formate  would  condense  with  a  thioether  of  ethyl  thio- 
glycollate,  HSCH2COOC2H5,  giving  an  a-mercapto  derivative 
of  /?-hydroxy  aery  lie  acid  (X). 

We  prepared,  for  our  experiments,  ethyl  benzylthiogly- 
collate1  and  now  find  that  ethyl  formate  condenses  smoothly 
with  this  ester,  in  presence  of  metallic  sodium,  giving  ethyl 
a-benzylmercapto-/?-hydroxy  aery  late  (XIII).  We  have  also 
condensed  ethyl  formate  with  ethyl  benzoylthiogly  collate,2 
C6H5COSCH2COOC2H5,  under  the  same  conditions,  but  have 
reserved  the  description  of  this  work  for  publication  in  another 
paper. 

The  sodium  salt  of  ethyl  a-benyzlmercapto-/?-hydroxy- 
acrylate  (XI)  condensed  smoothly  with  pseudoethylthio- 
urea,  in  an  aqueous  solution,  giving  2-ethylmercapto-5-benzyl- 
mercapto-6-oxypyrimidine  (XII).  This  new  condensation 
is  represented  by  the  following  equation: 

1  Gabriel:  Ber.  d.  chem.  Ges.,  12,  1641. 

2  Wheeler  and  Johnson:  THIS  JOURNAL,  26,  198. 


274  Johnson  and  Guest. 

NH2  COOC2H5 

C2H5S.C       +  CSCH2C6H5  = 

II  II 

NH 


NaOCH 
XI. 

NH 

C2HSSC 

II 

CSCH2C8H5  +  NaOH  +  C2H5OH. 

II 

II 
N- 

II 
CH 

XII. 

The  study  of  the  properties  of  this  pyrimidine  was  of  par- 
ticular interest  because  it  is  the  first  mercaptopyrimidine 
to  be  described  which  has  the  mercapto  group  linked  to  the 
5-position  of  the  pyrimidine  ring.  Our  previous  work  in 
this  laboratory  has  been  confined  to  the  study  of  2-  and 
4-  or  6-mercapto  derivatives.  The  5-mercapto  group  in  2- 
ethylmercapto-5-benzylmercapto-6-oxypyrimidine  (XII)  is 
very  firmly  bound  and  is  not  removed  by  hydrolysis  with  acids. 
When  the  pyrimidine  was  digested  with  concentrated  hydro- 
chloric acid,  it  was  converted  quantitatively  into  5-benzyl- 
mercaptouracil  (XV).  On  the  other  hand,  when  heated  above 
its  melting  point  in  a  stream  of  dry  hydrochloric  acid  gas, 
it  was  converted  smoothly  into  2-thio-5-benzylmercapto- 
6-oxypyrimidine  (XIV). 

2-Ethylmercapto-5-benzylmercapto-6-oxypyrimidine  reacted 
in  a  smooth  manner  with  phosphorus  oxychloride,  giving 
2-ethylmercapto-5-benzylmercapto-6-chlorpyrimidine  (XVI) . 
When  this  chlorpyrimidine  was  heated  with  ammonia,  a 
quantitative  yield  of  2-ethylmercapto-5-benzylmercapto-6- 
aminopyrimidine  (XVIII)  was  obtained.  This  compound 
was  then  converted  quantitatively  into  5-behzylmercapto- 
cytosine  (XVII)  by  hydrolysis  with  hydrochloric  acid.  These 
different  transformations  are  represented  by  the  following 
formulas : 


Researches  on  Pyrimidines. 

K     to § 


275 


co 


ro 
o 
a 
f» 


"U-i 


:s 

en 

f  a 

I  Q 


I 

P 

ffi 


ffi 

O 
o 

* 

:=o — ^      o 


M 


'rr 

o 


\ ' 

3—Q—2 


co     o  *    W 

?    I 

ffi          " 


a 


. 


There  are  7  possible  thiopyrimidines  that  can  be  derived 
from  5-hydroxyuracil  by  replacement  of  the  oxygen  atoms 
with  sulphur,  viz.,  the  three  monothio  derivatives,  2-thio-5- 
hydroxy-6-oxy-,  2,6-dioxy-5-mercapto-,  and  2-oxy-5-hydroxy- 
6-oxypyrimidines  (XIX,  XX,  XXI),  the  three  dithio  deriva- 
tives, 2,6-dithio-5-hydroxy-,  2-thio-5-mercapto-6-oxy-,  and  2- 
oxy-5-mercapto-6- thiopyrimidines  (XXII,  XXIII,  XXIV) , 
and  finally  2,6-dithio-5-mercaptopyrimidine  (XXV). 


276 


NH 


Johnson  and  Guest. 

NH CO 

CSH 


XXII. 


XXIV. 


NH CN 

XXV. 

5-Benzylmercaptouracil  (XV)  and  2-thio-5-benzylmercapto-6- 
oxypyrimidine  (XIV)  are  the  benzyl  ethers  of  2,6-dioxy-5- 
mercaptopyrimidine  (XX)  and  2-thio-5-mercapto-6-oxypy- 
rimidine  (XXIII),  respectively,  and  also  the  first  thio  ethers 
of  this  series  of  thiopyrimidines  to  be  described. 

We  have  prepared  the  first  member  of  the  series,  2-thio- 
5-hydroxy-6-oxypyrimidine  (XIX),  by  heating  2-methyl- 
mercapto-5-ethoxy-6-oxypyrimidine1  (XXVI)  in  a  stream 
of  dry  hydrochloric  acid  gas.2  An  attempt  was  also  made  to 
synthesize  2-oxy-5-hydroxy-6-thiopyrimidine  (XXI)  from  2- 
methylmercapto-5-ethoxy-6-oxypyrimidine.  The  latter  com- 
pound reacted  smoothly  with  phosphorus  oxychloride,  giv- 
ing 2-methylmercapto-5-ethoxy-6-chlorpyrimidine  (XXVIII), 
which  was  then  converted  into  2-methylmercapto-5-ethoxy-6- 
thiopyrimidine  (XXIX)  by  the  action  of  potassium  hydro- 
sulphide.  All  attempts  to  hydrolyze  this  pyrimidine  to  2- 
oxy-5-ethoxy-6-thiopyrimidine  and  2-oxy-5-hydroxy-6-thio- 
pyrimidine  (XXI)  were  unsuccessful.  The  6-sulphur  atom 
is  not  firmly  bound  and  the  pyrimidine  underwent  hydrolysis 
with  formation  of  methyl  mercaptan  and  hydrogen  sulphide 

1  Johnson  and  McCollum:  J.  Biol.  Chem.,  1,  447. 

2  Wheeler  and  Liddle:  J.  Am.  Chem.  Soc.,  30,  1157. 


Researches  on  Pyrimidines. 


277 


and  was  converted  into  5-ethoxyuracil  (XXX).  2,6-Dichlor- 
5-ethoxypyrimidine  (XXXII)  was  prepared  by  the  action 
of  phosphorus  oxychloride  on  5-ethoxyuracil  (XXX).  When 
this  dichlorpyrimidine  was  warmed  with  potassium  hydro- 
sulphide  it  was  converted  quantitatively  into  the  ethyl  ether 
of  2,6-dithio-5-hydroxypyrimidine  (XXIII)  or  2,6-dithio-5- 
ethoxypyrimidine  (XXXI).  These  various  transformations 
are  represented  by  the  following  formulas : 


O 


•H     O=O  -  O 

n    g    Q 


Ci 

a 


H  w 


•8- 


I 

=- 


O 


1=0—0 
I     O     Q 


o 

p 

M:dS|| 
B       f 

^0=0-0 

XXVI. 

\ 


S 


a 


—  O—  !z! 


278  Johnson  and  Guest. 

EXPERIMENTAL,  PART. 

Ethyl  Benzylthioglycollate,  C6H5CH2SCH2COOC2H5<— This  es- 
ter has  been  described  by  Gabriel,1  who  prepared  it  by  esteri- 
fication  of  benzylthioglycollic  acid  with  ethyl  alcohol.  We 
prepared  it  by  the  action  of  sodium  benzylmercaptide  on 
ethyl  chloracetate.  The  benzyl  mercaptan  was  dissolved 
in  alcohol  containing  a  molecular  proportion  of  sodium  ethylate 
and  the  required  amount  of  ethyl  chloracetate  added.  The 
solution  was  then  heated  on  the  steam  bath  until  it 5  failed 
to  give  an  alkaline  reaction,  cooled,  and  the  undissolved  sodium 
chloride  filtered  off.  The  excess  of  alcohol  was  then  removed 
by  heating  the  mixture  to  120°  and  the  crude  ester  washed 
with  water,  dissolved  in  the  ether,  and  dried  over  calcium 
chloride.  It  was  purified  by  one  distillation  under  diminished 
pressure  and  the  fraction  boiling  within  10  degrees  at  a  constant 
pressure  saved  for  our  experiments.  The  boiling  points  of 
four  different  preparations  were  i9O°-2OO°  at  30-33  mm., 
i85°-20o°  at  33  mm.,  i98°-2io°  at  50  mm.,  and  i79°-i89° 
at  23  mm.  Thirty- two,  35  and  72  grams  of  the  distilled  thio- 
glycollic  ester  were  obtained  from  34,  38  and  75  grams,  re- 
spectively, of  benzyl  mercaptan. 

Ethyl  a-Benzylmercapto-p-hydroxyacrylate, 
HOCH:C(SCH2C6H5)COOC2H5.— The  sodium  salt  of  this  ester 
was  prepared  by  adding  a  mixture  of  32  grams  of  ethyl  benzyl- 
thioglycollate  and  20  grams  of  ethyl  formate,  in  small  portions, 
to  dry  ether  in  which  was  suspended  4  grams  of  finely  divided 
sodium.  The  salt  began  to  deposit  at  once  as  a  yellow  powder, 
and  within  24  hours  the  sodium  had  completely  disappeared 
and  the  condensation  was  complete.  The  yield  of  crude  salt 
was  45  grams.  When  the  salt  was  dissolved  in  water  and  the 
solution  acidified  with  hydrochloric  acid  the  acrylic  ester 
separated  as  an  oil  which  solidified  when  cooled  at  o°.  After 
drying  in  a  vacuum  over  potassium  hydroxide  and  sulphuric 
acid  it  melted  at  57°-58°  to  a  clear  oil.  The  ester  was  very 
soluble  in  the  common  organic  solvents  and  reacted  with 
ferric  chloride,  giving  a  bright  red  color.  An  attempt  to  dis- 

1  Ber.  d.  chem.  Ges..  12,  1641. 


Researches  on  Pyrimidines.  279 

til  it  under  diminished  pressure  was  unsuccessful.  Sulphur 
determination  (Carius) :  0.2527  gram  substance  gave  0.2654 
gram  of  BaSO4. 

Calculated  for 
Ci2H14O8S.  Found. 

S  13.44  i4-4 

2-Ethylmercapto-5-benzylmercapto-6-oxy  pyrimidine, 
NH CO 

I  I 

C2H5SC  CSCH2CCH5. — Molecular    proportions    of  pseudo- 

N CH 

ethylthiourea  hydrobromide  (28  grams)  and  potassium  hy- 
droxide (8.5  grams)  were  dissolved  in  water  and  the  solutions 
added  successively  to  a  cold,  aqueous  solution  of  45  grams 
of  the  sodium  salt  of  ethyl  a-benzylmercapto-/?-hydroxy- 
acrylate.  The  mixture  was  then  allowed  to  stand  at  ordinary 
temperature  for  about  12-14  hours  and  heated  one  hour  on 
the  steam  bath  to  complete  the  reaction.  The  alkaline  solu- 
tion was  then  cooled,  filtered,  and  acidified  with  hydrochloric 
acid.  A  heavy  oil  separated  and  finally  crystallized  in  prisms, 
melting  at  i5O°-i53°  to  a  clear  oil.  The  weight  of  this  crude 
pyrimidine  was  10  grams,  and  2  grams  more  were  obtained  by 
extracting  the  acid  solution  with  ether.  The  pyrimidine  is 
insoluble  in  water  and  difficultly  soluble  in  ether.  It  crystallizes 
from  95  per  cent,  alcohol  in  four-  and  six-sided,  tabular  crystals, 
which  melt  at  i55°-i56°  to  a  clear  oil  without  effervescence. 
The  pyrimidine  dissolves  in  dilute  sodium  hydroxide  solution 
and  is  reprecipitated  unaltered  by  addition  of  acids.  Analysis 
(Kjeldahl) : 

Calculated  for 
CiaH^ONaSa.  Found. 

N  10.07  10.10 

NH CO 

I            I 
5-Benzylmercaptouracil,    CO        CSCH2CCH5. A  quantita- 

NH CH 

tive  yield   of   this  pyrimidine  was  obtained  by  digesting  2- 


280  Johnson  and  Guest. 

ethylmercapto-5-benzylmercapto-6-oxypyrimidine  (3  grams) 
with  strong  hydrochloric  acid  for  4  hours.  It  is  difficultly 
soluble  in  hot  water  and  cold  alcohol.  It  crystallizes  from 
boiling  95  per  cent,  alcohol  in  rhombic  plates  or  tables,  which 
melt  at  290°  to  a  clear  oil  with  decomposition.  They  gave 
a  strong  test  for  uracil  when  treated  with  bromine  water  and 
barium  hydroxide.  Analysis  (Kjeldahl) : 

Calculated  for 
CnHioOsNjS.  Found. 

N  11.96  n-74 

Five-tenths  gram  of  this  pyrimidine  was  heated  with  10  cc. 
of  concentrated  hydrochloric  acid  at  i3O°-i4o°  for  2  hours. 
It  was  recovered  unaltered  and  melting  sharply  at  290°. 
The  pyrimidine  was  then  heated  again  at  i6o°-i7o°  for  3 
hours,  when  it  had  been  partly  decomposed.  However,  even 
after  this  energetic  treatment,  a  small  amount  of  the  pyrimi- 
dine was  recovered  unaltered  and  melting  at  290°. 

This  pyrimidine  also  dissolves  in  boiling  aniline  without 
change  and  separates  on  cooling  in  plates  melting  at  290°. 

2-Ethylmercapto-i)-benzylmercapto-6-chlor pyrimidine, 
N== CC1 

I  I 

C2H5SC          CSCH2CttH5.— 2-Bthylmercapto-5-benzylmercapto- 

II  II 
N CH 

6-oxypyrimidine  reacts  smoothly  with  phosphorus  oxychloride, 
giving  this  chlorpyrimidine.  Ten  grams  of  the  mercapto- 
pyrimidine  and  40  cc.  of  phosphorus  oxychloride  were  heated 
at  120°  for  45  minutes,  when  the  evolution  of  hydrochloric 
acid  had  practically  ceased.  The  excess  of  phosphorus  halide 
was  then  expelled  by  heating  at  100°  under  diminished  pres- 
sure, when  a  viscous  oil  was  obtained.  This  was  poured 
into  water,  warmed  gently  to  decompose  any  double  compound 
of  phosphorus  oxychloride,  and  then  extracted  with  ether. 
After  drying  over  calcium  chloride  and  evaporating  the  ether, 
we  obtained  the  chlorpyrimidine  in  the  form  of  a  dark  oil. 
This  solidified  on  cooling  and  melted  at  4O°-45°.  The  pyrimi- 
dine crystallizes  from  ligroin  in  prisms  melting  at  47°-48° 


Researches  on  Pyrimidines. 


281 


to  a  clear  oil.     It  is  extremely  soluble  in  benzene  and  alcohol, 
but  insoluble  in  water.     Analysis  (Kjeldahl)  : 


Calculated  for 
C13Hi3N2ClS8. 


Found. 

9.8 


N  9.44 

2-Ethylmercapto-5-benzylmercapto-6-aminopyrimidine, 


C2H5SC        CSCH3CCH5.— A  quantitative  yield  of  this  pyrimi- 

II         II 
N CH 

dine  was  obtained  when  5  grams  of  the  above  chlorpyrimidine 
were  heated  with  an  excess  of  an  alcoholic  solution  of  ammonia, 
at  I20°-i4o°,  for  2  hours.  After  evaporating  the  excess  of 
alcohol  at  100°,  the  pyrimidine  was  then  separated  from 
ammonium  chloride  by  dissolving  it  in  ether.  It  is  very 
soluble  in  ether,  ligroin,  alcohol  and  benzene,  but  insoluble  in 
water.  It  crystallizes  from  ligroin  in  sheaves  of  needles 
melting  at  68°-69°  to  a  clear  oil.  Analysis  (Kjeldahl): 


N 


Calculated  for 

C13H16N8S2. 

I5.I6 


Found 
14.88 


5-Benzylmercaptocytosine,    CO      CSCH2C6H5.  —  Five    grams 

NH— CH 

of  2-ethylmercapto-5-benzylmercapto-6-aminopyrimidine  were 
dissolved  in  50  cc.  of  strong  hydrochloric  acid  and  the  solution 
boiled  for  1.5  hours,  when  the  evolution  of  ethyl  mercaptan 
had  practically  ceased.  The  solution  was  then  evaporated 
to  dryness,  the  hydrochloride  dissolved  in  water,  and  the 
pyrimidine  base  precipitated  by  addition  of  ammonia.  It  is 
soluble  in  hot  alcohol  and  insoluble  in  water  and  ether.  It 
crystallizes  from  95  per  cent,  alcohol  in  plates  melting  at 
240°-24i°.  Analysis  (Kjeldahl) : 


N 


Calculated  for 
CuHnONsS. 

I8.0I 


Found. 
iS.OO 


282  Johnson  and  Guest. 

2-Thio-5-benzylmercapto-6-oxypyrimidine, 
NH CO 

CS        CSCH2C6H5. — Seven-tenths  gram  of  2-ethylmercapto-5- 

NH CH 

benzylmercapto-6-oxypyrimidine  was  heated  in  a  current  of 
dry  hydrochloric  acid  gas,  at  i6o°-i7o°,  until  the  evolution 
of  ethyl  chloride  ceased.  We  obtained  a  brown  substance, 
which  was  washed  with  ether  to  remove  traces  of  oil  and  then 
crystallized  from  95  per  cent,  alcohol.  The  pyrimidine  sepa- 
rated, on  cooling,  in  blocks  melting  at  i95°-i96°  to  an  oil 
without  effervescence.  It  gave  a  strong  test  for  sulphur. 
Analysis  (Kjeldahl) : 

Calculated  for 
CnH10ON2S.  C4H4ONjSj.  Found. 

N  11.20  17.50  11.57 

Attempts  to  prepare  this  pyrimidine  by  condensation  of 
the  sodium  salt  of  ethyl  a-benzylmercapto-/?-hydroxyacrylate 
with  thiourea  in  aqueous  solution,  and  in  alcohol  in  presence 
of  sodium  ethylate,  were  unsuccessful.  For  example:  one  gram 
of  sodium  and  3  grams  of  thiourea  were  dissolved  in  alcohol, 
ten  grams  of  the  sodium  salt  suspended  in  the  solution,  and 
the  mixture  then  digested  on  the  steam  bath  for  6  hours.  There 
was  no  indication  of  any  reaction  and  8.0  grams  of  the  unaltered 
sodium  salt  separated  on  cooling.  The  alcohol  filtrate  was 
then  evaporated  to  dryness  and  the  residue  left  behind  dis- 
solved in  a  little  cold  water  and  the  solution  carefully  acidified 
with  hydrochloric  acid.  The  solution  became  turbid,  but  on 
standing  no  pyrimidine  separated,  showing  that  no  condensa- 
tion had  taken  place. 

2-Methylmercapto- 5- ethoxy-6-chlor  pyrimidine, 
N==CC1 

I  I 

CH3SC         COC2H5. — Twenty-five  grams  of  2-methylmercapto- 

N CH 

S-ethoxy-G-oxypyrimidine1  were  suspended  in  40  cc.  of  phos- 

1  Johnson  and  McCollum:  Loc.  cit. 


Researches  on  Pyrimidines.  283 

phorus  oxychloride.  There  was  an  immediate  reaction  and 
the  pyrimidine  dissolved  completely.  The  solution  was 
heated  in  an  oil  bath  at  120°- 130°  for  a  few  hours  to  complete 
the  reaction,  and  the  excess  of  phosphorus  oxychloride  re- 
moved by  heating  at  100°  under  diminished  pressure.  An 
oil  was  obtained  which  immediately  solidified  when  poured 
into  cold  water.  This  was  a  double  compound  of  the  pyrimi- 
dine and  phosphorus  oxychloride,  and  in  order  to  decompose 
it  and  destroy  the  phosphorus  halide,  it  was  necessary  to 
triturate  it  with  hot  water.  The  pyrimidine  was  then  dis- 
solved in  ether,  washed  with  dilute  sodium  hydroxide  solution 
and  dried  over  calcium  chloride.  When  the  ether  was  removed 
we  obtained  the  pyrimidine  as  a  crystalline  solid  melting  at 
70°.  The  yield  was  21  grams,  or  95  per  cent,  of  the  calculated. 
The  pyrimidine  is  insoluble  in  water  and  very  soluble  in  ben- 
zene and  ether.  It  crystallizes  from  95  per  cent,  alcohol 
in  slender  prisms  melting  at  75°  to  an  oil.  Analysis  (Kjel- 
dahl) : 

Calculated  for 

C7HoON2ClS.  Found. 

N  13.69  13.63 

2-Methylmercapto-5-ethoxy-6-thiopyrimidine, 
NH CS 

I  I 

CH3SC  COC2H5.— The  potassium  salt  of  this  pyrimidine 

II  II 
N CH 

was  obtained  when  5  grams  of  2-methylmercapto-5-ethoxy- 
6-chlorpyrimidine  were  dissolved  in  an  alcoholic  solution  of 
potassium  hydrosulphide  and  the  mixture  digested  on  the 
steam  bath  for  several  hours.  The  excess  of  alcohol  was 
then  removed  by  evaporation  at  100°  and  the  potassium 
salt  of  the  pyrimidine  and  potassium  chloride  dissolved  in 
water.  When  this  solution  was  acidified  with  acetic  acid, 
the  6-thiopyrimidine  separated  in  yellow  crystals.  It  is 
difficultly  soluble  in  hot  water  but  crystallizes  from  alcohol 
in  light  yellow  prisms  melting  at  190°  to  a  clear  oil.  The 
yield  was  3.5  grams.  Analysis  (Kjeldahl) : 


284  Johnson  and  Guest. 

Calculated  for 
C7HioON2S2.  Found. 

N  13.86  13.78 

An  attempt  to  prepare  2-oxy-5-ethoxy-6-thiopyrimidine 
from  this  compound,  by  hydrolysis  with  hydrochloric  acid, 
was  unsuccessful.  About  7  grams  of  the  mercaptopyrimidine 
were  digested  with  a  large  excess  of  concentrated  hydrochloric 
acid  on  the  steam  bath  for  several  hours.  Methyl  mercaptan 
and  hydrogen  sulphide  were  evolved  and  the  pyrimidine 
finally  dissolved.  The  acid  solution  was  then  evaporated  to 
dryness  and  the  crystalline  substance  obtained  purified  by 
repeated  crystallizations  from  hot  water.  It  separated  in 
irregular  prisms  which  melted  at  about  275°  to  a  dark  oil. 
This  melting  point  varies  according  to  the  rate  of  heating. 
The  compound  gave  no  test  for  sulphur,  and  a  nitrogen  de- 
termination (Kjeldahl)  agreed  with  the  calculated  value 
for  5-ethoxyuracil.1  The  small  amount  of  material  which 
accompanied  this  5-ethoxypyrimidine  and  rendered  the  puri- 
fication difficult  contained  sulphur,  but  we  did  not  succeed 
in  isolating  a  sufficient  quantity  of  the  substance  in  pure  state 
for  analysis.  Its  melting  point,  i9O°-23O°,  indicated  a  mix- 
ture. 

Calculated  for 

C6H8O8N2.  Found. 

N  17-94  17.80 


2,  6-Dichlor-  5-ethoxypyrimidine,  Cl.C          COC2H5.  —  Thispyr- 

II  II 

N  -  CH 

imidine  was  prepared  by  the  action  of  phosphorus  oxychloride 
on  5-ethoxyuracil.1  Twelve  grams  of  the  ethoxyuracil  and 
70  cc.  of  phosphorus  oxychloride  were  digested  at  120°-  130° 
for  nearly  3  hours  before  the  evolution  of  hydrochloric  acid 
ceased.  The  dark  liquid  was  then  filtered  from  a  small  amount 
of  insoluble,  amorphous  substance  and  the  excess  of  phosphorus 
halide  removed,  in  the  usual  manner,  by  heating  at  100° 
under  diminished  pressure.  We  obtained  a  thick  syrup 

1  Johnson  and  McCollum:  Loc.  cit. 


Researches  on  Pyrimidines.  285 

which  solidified  when  poured  into  cold  water.  In  order  to 
destroy  all  phosphorus  halide,  this  substance  was  then  melted 
under  water  by  heating  the  liquid  to  6o°-7o°,  and  after  thor- 
ough mixing  the  pyrimidine  was  dissolved  in  ether.  The 
ether  solution  was  then  dried  over  calcium  chloride  and  the 
excess  of  ether  removed  by  spontaneous  evaporation,  when 
the  pyrimidine  separated  in  well-developed  prisms.  It  is 
soluble  in  cold  alcohol,  benzene  and  petroleum  ether  and 
crystallizes  from  the  latter  in  clusters  of  radiating  prisms 
and  needles  which  melt  at  4i°-42°  to  a  clear  oil.  It  crystal- 
lizes from  water  in  prisms  melting  at  the  same  temperature. 
The  yield  was  about  75  per  cent,  of  the  calculated.  Analysis 
(Kjeldahl) : 

Calculated  for 
C6H6ON2C12.  Found. 

N  14-50  14-35 

2, 6-Diihio-5-eihoxy pyrimidine  (5-Ethoxydithiouracil) , 
NH CS 

I  I 

CS        COC2H5. — This  compound  was  prepared  by  the  action 

NH CH 

of  potassium  hydrosulphide  on  2,6-dichlor-5-ethoxypyrimidine 
in  alcoholic  solution.  It  is  soluble  in  hot  alcohol  and  crystal- 
lizes, on  cooling,  in  needles  which  slowly  decompose  when 
heated  above  255°,  and  effervesce  violently  at  about  267°— 
268°.  The  pyrimidine  is  insoluble  in  water.  Analysis  (Kjel- 
dahl) : 

Calculated  for 
C6H8ON2S2.  Found. 

N  14.7  14.9 

Sodium  Salt  of  Ethyl  a-Phenoxy-fi-hydroxyacrylate, 
NaOCH:C(OC6H5)COOC2H5.— Johnson  and  Heyl1  prepared 
this  salt  by  condensation  of  ethyl  formate  with  ethyl  phenoxy- 
acetate  in  presence  of  sodium  ethylate.  The  use  of  sodium 
ethylate  is  unnecessary  and  a  practically  quantitative  yield 
of  the  salt  can  be  obtained  if  the  esters  are  condensed  in  ether 
in  the  presence  of  metallic  sodium.  Thirty-one  grams  of 

1  THIS  JOURNAL,  37,  636. 


2  86  Johnson  and  Guest. 

crude,  dry  salt  were  obtained  from  25  grams  of  ethyl  phenoxy- 
acetate. 

NH CO 

2-Thio-$-phenoxy-6-oxy  pyrimidine,     CS        COC6H5.  —  John- 

NH  — CH 

son  and  Heyl1  have  shown  that  the  above  sodium  salt  con- 
denses with  pseudoethylthiourea,  in  aqueous  solution,  giving 
2-ethylmercapto-5-phenoxy-6-oxypyrimidine.  Fifteen  grams 
of  thiourea  and  4.5  grams  of  sodium  were  dissolved  in  alcohol 
and  31  grams  of  the  sodium  salt  dissolved  in  the  solution  by 
warming  on  the  steam  bath.  After  digesting  for  10  hours, 
the  excess  of  alcohol  was  removed  by  evaporation  at  100° 
and  the  residue  remaining  dissolved  in  cold  water,  filtered, 
and  the  solution  acidified  with  acetic  acid.  Sixteen  grams 
of  the  crude  pyrimidine  separated  as  a  colorless,  granular 
powder.  It  is  insoluble  in  hot  water,  moderately  soluble 
in  alcohol,  insoluble  in  benzene  and  soluble  in  acetic  acid. 
It  crystallizes  from  acetic  acid  in  clusters  of  prisms  showing 
a  twinning  habit,  and  melts  at  253  °-254°  to  a  brown  oil.  Nitro- 
gen (Kjeldahl)  and  sulphur  (Carius)  determinations  gave  the 
following  results: 

Calculated  for  Found. 

Ci0H8OjN2S.  I.  II. 

N  12.73  12.82 

3  J4-56  14-30  H-72 

NH CO 

5-Phenoxyuracil,  CO        COC8H5.  —  This  pyrimidine  was  pre- 

NH CH 

pared  by  heating  2-thio-5-phenoxy-6-oxypyrimidine  (2  grams) 
with  concentrated  hydrochloric  acid  (35  cc.)  at  i4O°-i6o°, 
and  also  by  digestion  with  hydrobromic  acid  for  several  hours. 
It  is  practically  insoluble  in  cold  water  and  alcohol  and  difficultly 
soluble  in  hot  water.  It  crystallizes  from  boiling  acetic  acid 

i  Loc.  cit. 


Researches  on  Pyrimidines.  287 

in  distorted  needles  melting  at  290°  with  effervescence.     Analy- 
sis (Kjeldahl) : 

Calculated  for 
C10H8OjN3.  Found. 

N  13-72  13-62 

NEW  HAVEN,  CONN., 
June,  1909. 


[Reprinted  from  The  American  Chemical  Journal, 
Vol.  XVI.    No.  4.    October,  1909.] 


[Contributions  from  the  Sheffield  Laboratory  of  Yale  University.] 

CLXXL— RESEARCHES  ON  PYRIMIDINES: 

DIMETHYL   DERIVATIVES   OF  2-AMINOPYRIMIDINE. 

PREPARATION  OF  2-METHYLAMINO-5-METHYL- 

PYRIMIDINE. 

[FORTY-SIXTH   PAPER.] 
BY  TREAT   B.   JOHNSON  AND  KENNETH  G.   MACKENZIE.1 

This  paper  is  a  preliminary  contribution  to  the  study  of 
aminomethylpyrimidines  having  the  empirical  formula 
C6H9N3.  Our  interest  in  aminopyrimidines  of  this  compo- 
sition was  incited  by  a  paper  entitled  "Ueber  die  chemische 
Zusammensetzung  der  japanischen  Soja-Souce  oder  Schoyu,"2 
in  which  the  authors  have  described  two  decomposition  products 
of  Schdyu  to  which  they  have  assigned  the  empirical 
formulas  C6H9N3  and  C4H12N2.  They  state  that  the  substance, 
C6H9N3,  is  probably  an  isorner  of  aminodimethylpyrimidine, 
but  is  not  identical  with  any  one  of  three  pyrimidines  of  this 
constitution  which  have  been  described  in  the  literature,8 
mz.y  2,6-dimethyl-4-aminopyrimidine,4  2-amino-4,5-dimethyl- 
pyrimidine,5  and  2-amino-4,6-dimethylpyrimidine.6 

1  A  part  of  this  paper  was  presented  as  a  thesis  by  Mr.  Kenneth  Gerard  Mackenzie 
to  the  Faculty  of  the  Graduate  School  of  Yale  University  for  the  Degree  of  Master  of 
Science  (June,  1909). 

2  Suzuki,  Aso,  and  Mitarai:  Bull.  Coll.  Agriculture  (Tokio  Univ.),  7,  477  (1907). 

3  The  Japanese  investigators  failed  to  recognize  that  a  fourth  isomer,  4,5-dimethyl- 
6-aminopyrimidine,  has  been  prepared  by  Schlenker  (Ber.  d.  chem.  Ges.,  34,  2823). 
No  salts  of  this  pyrimidine  have  been  described. — T.  B.  J. 

4Schwarze:  J.  prakt.  Chem.,  42,   1    (1889).     Schmidt:  Ber.  d.   chem.  Ges.,  35 
1577  (1902). 

6  Schlenker:  Ber.  d.  chem.  Ges.,  34,  2819  (1901). 
6  Angerstein:  Ber.  d.  chem.  Ges.,  34,  3962. 


354  Johnson  and  Mackenzie. 

If  we  disregard  the  tautomeric  form  of  2-aminopyrimidine1 
(II),  there  are  only  five  possible  dimethyl  derivatives  of  this 
pyrimidine  (1),  viz.,  the  two  isomers  described  in  the  litera- 
ture, 4,5-dimethyl2-  and  4,6-dimethyl-2-aminopyrimidine3 
(III  and  IV),  2-methylamino-5-methylpyrimidine  (V), 
2-methylamino-4-methylpyrimidine  (VI),  and  2-dimethyl- 
aminopyrimidine  (VII). 


H2N.C         CH  HN= C         CH 

II  II  II  II 

N CH  HN CH 

I.  II. 

N=CH  N=CCH3 

H2NC         CH 

II  II 

N CCH3 

IV. 

N=< 

CH3HNC          CCH3    CH3HNC         CH        (CH3)2NC         CH 

.       II          II  II  II 

N CH  N CCH3 

V.  vi. 

We  shall  describe,  in  this  paper,  the  preparation  and  prop- 
erties of  2-methylamino-5-methylpyrimidine  (V),  and  also 
some  derivatives  of  the  isomeric  2-methylamino-4-methyl- 
pyrimidine  (VI).  A  description  of  a  new  method  of  pre- 
paring thymine  has  also  been  appended  to  this  paper. 

It  has  been  shown  in  several  papers  from  this  laboratory* 
that  aryl  substituted  aminopyrimidines  can  be  obtained,  in 
practically  quantitative  yields,  by  heating  2-mercaptopyr- 
imidines  with  aromatic  bases.  The  action  of  aliphatic  amines 
on  mercaptopyrimidines  has  not  been  investigated.  Since 

1  Biittner:  Ber.  d.  chem.  Ges.,  36,  2229. 

2  Schlenker:  Loc.  cit. 

3  Angerstein:  Loc.  cit. 

4  Wheeler  and  Bristol:  THIS  JOURNAL,  33,  438,  448.     Johnson  and  Johns:  Ibid., 
34,  175.     Johnson  and  Heyl:  Ibid.,  38,  238.     Johnson  and  Storey:  Ibid.,  40,  131. 


Researches  on  Pyrimidines.  355 

it  was  necessary  for  us  to  devise  a  practical  method  of  pre- 
paring alphylaminopyrimidines  easily  and  in  sufficient  quan- 
tities for  our  work,  we  therefore  investigated  the  action  of 
methylamine  on  some  2-mercaptopyrimidines. 

We  now  find  that  2-methylmercapto-5-methyl-6-oxypyr- 
imidine1  (VIII),  and  2-methylmercapto-4-methyl-6-oxypyr- 
imidine2  (IX),  react  with  methylamine  at  i4o°-i5O°,  giving 
quantitative  yields  of  2-methylamino-5-methyl-6-oxypyrimi- 
dine  (X)  and  2-methylamino-4-methyl-6-oxypyrimidine  (XI), 
respectively.  The  latter  pyrimidine  was  identical  with  the 
2-methylaminopyrimidine  obtained  by  Jager3  by  alkylation 
of  2-amino-4-methyl-6-oxypyrimidine4  with  methyl  iodide. 
The  same  pyrimidine  has  also  recently  been  prepared  by 
Majima5  by  condensing  methylguanidine  with  ethyl  aceto- 
acetate.  The  yield  by  this  method,  however,  corresponds 
to  only  about  50  per  cent,  of  the  theoretical,  because  part  of 
the  methylguanidine  condenses,  giving  the  isomeric  2-amino- 
3,4-dimethyl-6-oxypyrimidine. 

These  two  2-methylaminopyrimidines,  (X)  and  (XI), 
reacted  smoothly  with  phosphorus  oxychloride,  giving  prac- 
tically quantitative  yields  of  2-methylamino-5-methyl-6-chlor- 
pyrimidine  (XII)  and  2-methylamino-4-inethyl-6-chlorpyr- 
imidine  (XIII),  respectively.  Both  of  these  pyrimidines 
underwent  hydrolysis  to  the  original  6-oxypyrimidines  (X) 
and  (XI),  when  an  attempt  was  made  to  reduce  them  with 
hydriodic  acid.  On  the  other  hand,  they  were  converted 
into  2-methylamino-5-methylpyrimidine  (V)  and  2-methyl- 
amino-4-methylpyrimidine  (VI),  respectively,  by  reduction 
with  zinc  dust.  We  have  not  isolated  the  free  2-methyl- 
amino-4-methylpyrimidine,6  but  have  procured  evidence  of 
its  formation,  since  we  have  obtained  a  picrate  of  the  base 
and  a  characteristic  zinc  chloride  double  compound  of  definite 

1  Wheeler  and  Merriam:  THIS  JOURNAL,  29,  487. 

2  List:  Ann.  Chem.  (Liebig),  236,  12. 
»  Ann.  Chem.  (Liebig),  262,  365. 

4  Jager:  Loc.  cit.     Kohler:  Ber.  d.  chem.  Ges.,  19,  220. 

6  Ber.  d.  chem.  Ges.,  41,  176. 

6  We  were  obliged  to  discontinue  experiments  on  the  reduction  of  2-methylamino- 
4-methyl-6-chlorpyrimidine,  because  of  the  unexpected  departure  of  one  of  us  from 
the  laboratory  and  on  account  of  pressure  of  other  work. — T.  B.  J. 


356 


Johnson  and  Mackenzie. 


constitution.  The  experimental  evidence  indicates  that  this 
methylaminopyrimidine  is  not  identical  with  the  base  found 
in  Schdyu. 


NH CO 

I  I 

CH3SC 

II 

N- 


CCH< 

II 
CH 


VIII. 


NH- 

CH3SC 

II 
N  — 


CO 


IX. 


CCH3 


NH CO 

I  I 

CH3HNC  CCH8 


N- 


X. 


CH 


i 

N  ==  CC1 


CH3HNC 

II 
N 


CCH, 

II 
CH 


XII. 


NH CO 

I  1 
CH3HNC          CH 

II  II 

N CCH, 

XI. 


CH3HNC 


N  ==  CC1 

I  I 

CH 


N 


CCH3 


XIII. 


CH3HNC 


CCH, 


CH,HNC 


CH 


N  --  CH  N  --  CCH3 

V.  VI. 

2-Methylamino-5-methylpyrimidine  (V)  is  not  identical 
with  the  base  C6H9N3  which  Suzuki  and  his  coworkers  isolated 
from  Schdyu.  They  state  that  their  base  reacted  with  diazo- 
benzenesulphonic  acid,  in  the  presence  of  alkali,  giving  an 
intense  red  color.  Our  pyrimidine  and  the  diazo  reagent 
gave  at  first  no  color,  but  on  long  standing  a  brilliant  red 
color  finally  developed.  A  characteristic  feature  of  their 
base  was  its  tendency  to  form  acid  salts,  viz.,  the  picrate 


Researches  on  Pyrimidines.  357 

C6H9N3(C6H3O7N3)2,  decomposing  at  230°,  and  the  hydrochloride 
C6H9N3.2HC1,  melting  at  232°-233°.  Our  pyrimidines,  on 
the  other  hand,  are  characterized  by  their  tendency  to  form 
basic  salts.  The  isomeric  picrates,  (C6H9N3)2.C6H3O7N3,  of 
2-methylamino-5-methylpyrimidine  and  2-methylamino-4- 
methylpyrimidine  both  decomposed  when  heated  above 
150°.  2-Methylamino-5-methylpyrimidine  formed  a  hydrous 
hydrochloride,  (C6H9N3)2HC1.H2O,  melting  at  i62°-i63°.  It 
is  an  interesting  fact  that  2-amino-5,6-dimethylpyrimidine1 
is  the  only  dimethyl  derivative  of  2-aminopyrimidine,  so 
far  examined,  that  forms  acid  salts,  viz.,  the  picrate  and  hy- 
drochloride. 

A  New  Method  of  Preparing  Thymine. 

In  a  previous  paper  from  this  laboratory  one  of  the  writers2 
showed  that  pseudomethylthiourea  condenses  smoothly,  in 
aqueous  solution,  with  the  sodium  salt  of  diethyl  oxalpro- 
pionate,  giving  2-methylmercapto-4-carboxyl-5-methyl-6-oxy- 
pyrimidine.  When  this  acid,  in  small  quantities,  is  heated 
above  its  melting  point  it  undergoes  a  quantitative  decom- 
position, with  evolution  of  carbon  dioxide,  giving  2-methyl- 
mercapto-5-methyl-6-oxypyrimidine.3  A  quantitative  yield 
of  thy  mine  is  then  obtained  by  hydrolysis  of  tMs  mercapto- 
pyrimidine.  The  writer  did  not,  at  that  time,  lay  stress  on 
this  method  of  synthesizing  thymine  because  of  the  progress 
of  other  work  in  this  laboratory  on  different  methods  of  pre- 
paring this  pyrimidine. 

We  have  now  investigated  this  method  of  preparation  and 
find  that  the  sodium  salt  of  diethyl  oxalpropionate  condenses 
as  smoothly,  in  aqueous  solution,  with  pseudoethylthiourea 
as  with  pseudomethylthiourea,  giving  the  corresponding 
2-ethylmercapto-4-carboxyl-5-methyl-6-oxypyrimidine  (XIV) . 
This  pyrimidine  melts  lower  than  the  corresponding  2-methyl- 
mercapto  compound4  and  undergoes  decomposition  at  its 
melting  point,  giving  2-ethylmercapto-5-methyl-6-oxypyrimi- 

1  Loc.  cit. 

2  Johnson:  J.  Biol.  Chem.,  3,  299  (1907). 

3  Wheeler  and  Merriam:  Loc.  cit. 

4  Johnson:  Loc.  cit. 


358  -Johnson  and  Mackenzie. 

dine1  (XV),  which  can  be  converted  into  thymine  (XVI) 
by  hydrolysis  with  hydrochloric  acid.  The  success  of  this 
method  of  preparation  was  evidently  dependent  upon  the 
fact  whether  large  amounts  of  the  mercapto  acid  (XIV) 
could  be  changed  smoothly  and  quantitatively  into  2-ethyl- 
mercapto-5-methyl-6-oxypyrimidine.2  Working  with  small 
quantities,  less  than  15-16  grams  of  the  acid,  the  decompo- 
sition into  2-ethylmercapto-5-methyl-6-oxypyrimidine  was 
practically  quantitative  and  the  final  yield  of  thymine  corre- 
sponded to  nearly  85-90  per  cent,  of  the  theoretical.  On 
the  other  hand,  when  large  amounts  of  2-ethylmercapto-4- 
carboxyl-5-methyl-6-oxypyrimidine  are  decomposed  under  the 
same  conditions  the  method  is  not  practicable  because  it  is 
then  necessary  to  heat  a  long  time,  at  a  high  temperature, 
in  order  to  complete  the  reaction.  Under  such  conditions 
secondary  reactions  set  in  with  formation  of  products  which 
contaminate  the  2-ethylmercapto-5-methyl-6-oxypyrimidine 
and  render  its  purification  difficult.  It  is  probable  that 
these  mercaptopyrimidines,  when  heated  at  high  temperatures 
and  in  presence  of  impurities,  slowly  undergo  dissociation  into 
ethylene  hydrocarbons  and  2-thiopyrimidines.  The  ethyl 
ester  of  2-ethylmercapto-4-carboxyl-5-methyl-6-oxypyrimidine 
(XVII)  was  obtained  in  one  experiment  as  the  chief  product 
of  the  condensation.  It  was  also  formed  quantitatively  by 
the  action  of  ethyl  iodide  on  the  silver  salt  of  the  mercapto 
acid  (XIV).  When  the  mercapto  acid  (XIV)  was  heated 
with  methylamine,  a  quantitative  yield  of  2-methylamino- 
4-carboxyl-5-methyl-6-oxypyrimidine  (XVIII)  was  obtained. 
These  various  transformations  are  represented  by  the  follow- 
ing formulas : 

1  Wheeler  and  Johnson:  THIS  JOURNAL,  31,  595. 

.  cit,  t 


Researches  on  Pyrimidines. 


359 


PART. 


2-Methylamino-5-methyl-6-oxypyrimidme, 
NH  -  CO 

I  I 

CH3HNC  CCH3.  —  Ten    grams    of    2-methylmercapto-5- 

II  II 
N  --  CH 

methyl-6-oxypyrimidine1  were  heated  with  18  grams  of  33  per 
cent,  methylamine  solution  (6  grams  CH3NH2)  at  140°-  150°  for 
two  hours.  The  clear  solution  was  then  transferred  to  a  dis- 

1  Loc.  cit. 


360  Johnson  and  Mackenzie. 

tillation  flask  and  the  excess  of  methylamine  expelled  by 
passing  a  current  of  air  through  the  boiling  solution.  On 
cooling,  8  grams  of  the  aminopyrimidine  separated,  corre- 
sponding to  91  per  cent,  of  the  theoretical  yield.  In  two  other 
experiments,  when  6  grams  of  the  2-methylmercaptopyr- 
imidine  were  heated  with  7.2  grams  of  33  per  cent,  methyl- 
amine solution,  under  the  same  conditions,  we  obtained  5.0 
and  5.3  grams  of  the  crude  pyrimidine. 

This  2-methylaminopyrimidine  is  difficultly  soluble  in  cold, 
but  very  soluble  in  hot  water;  soluble  in  boiling  alcohol  and 
benzene.  It  crystallizes  from  water  in  colorless,  hairy  crys- 
tals, which  melt  at  213°  to  a  clear  oil.  The  pyrimidine  is 
characterized  by  its  tendency  to  form  supersaturated,  aqueous 
solutions.  It  reacts  with  diazobenzenesulphonic  acid  in 
presence  of  sodium  hydroxide,  giving  a  strong,  claret-red 
color.  It  contained  one  molecule  of  water  of  crystallization, 
which  was  determined  by  heating  at  ioo°-uo°  for  one  hour. 

0.5821  gram  substance  lost  0.0584  gram  H2O. 

Calculated  for 

C6HgON3.HsO.  Found. 

H2O  11.4  10.03 

Nitrogen  determination  in  anhydrous  substance  (Kjeldahl) : 

Calculated  for 

C6H9ON3.  Found. 

N  30.22  30.23 

Sulphate,  C6H9ON3.H2SO4.— Five- tenths  gram  of  the  pyr- 
imidine base  and  0.7  gram  of  sulphuric  acid  were  dissolved 
in  water  and  the  solution  allowed  to  concentrate  in  the  air. 
The  salt  finally  crystallized  in  large,  transparent,  tabular 
crystals,  which  melted  at  202°  to  a  brown  oil.  The  salt  is 
insoluble  in  alcohol  but  very  soluble  in  water.  It  was  dried 
at  100°  for  analysis  (Kjeldahl): 

Calculated  for  Found. 

C6H9ON8.H»S04.  I.  II. 

N  17.72  17.51  17.83 

Picrate,  (C6H9ON3)2.C6H3O7N3.H2O.— This  salt  was  pre- 
pared by  adding  a  solution  of  picric  acid  to  an  aqueous  solu- 
tion of  the  base.  The  picrate  deposited  in  distorted  prisms 


Researches  on  Pyrimidines*  361 

which  melted  with  decomposition  at  240°.     Analysis  (Kjel- 
dahl)  : 

Calculated  for  C6H9ON3.CCH3O7N3  =  22  .82  per  cent  N. 

Calculated  for  C6H8ON3.(C6H3O7N3)2  =  21  .  10  per  cent  N. 

Calculated  for  (C6H9ON3)2.C6H3O7N8.H2O    =  24  .  oo  per  cent  N. 

I.  II.  III.  IV. 

Nitrogen  found  :  23.89          24.12          24.20          24.25 

Platinum   Chloride  Salt,    (C6H9ON3.HCl)2.PtCl4,     was    pre- 
pared by  addition  of  hydrochloroplatinic  acid  to  an  aqueous 
solution  of  the  pyrimidine  base.     It  did  not  contain  water 
of  crystallization.     Platinum  determinations: 
I.  0.0889  gram  of  salt  gave  0.0248  gram  of  Pt. 

II.  0.0989  gram  of  salt  gave  0.0277  gram  of  Pt. 

Calculated  for  Pound. 

(C6H9ON».HCl)2.PtCl4.  I.  II. 

Pt  28.3  27.90  28.06 

2-Methylamino-5-methyl-6-chlor  pyrimidine, 


I  I 

CHSHNC         CCH3.—  Six  and  five-tenths  grams  of  2-methyl- 

II  II 
N  --  CH 

amino-5-methyl-6-oxypyrimidine  were  dissolved,  by  warm- 
ing, in  30  cc.  of  phosphorus  oxychloride  and  the  solution  boiled 
for  30  minutes.  The  excess  of  phosphorus  oxychloride  was 
then  removed  by  heating  at  100°  under  diminished  pressure, 
when  a  viscous  liquid  was  obtained.  This  was  dissolved 
in  cold  water  and  the  solution  made  alkaline  with  sodium 
hydroxide,  when  the  chlorpyrimidine  separated.  After  dry- 
ing in  a  vacuum  over  concentrated  sulphuric  acid  it  weighed 
6.9  grams,  corresponding  to  95  per  cent,  of  the  theoretical. 
In  a  second  experiment,  when  we  used  10.6  grams  of  the 
2-methylmercaptopyrimidine  and  53  cc.  of  phosphorus  oxy- 
chloride we  obtained  a  yield  of  11.5  grams  of  the  chlorpyr- 
imidine. 

The  pyrimidine  is  insoluble  in  water  but  soluble  in  alcohol 
and  benzene.     It  sublimes  at  100°  and  melts  at  131°  to  a 


362  Johnson  and  Mackenzie. 

clear  oil  with  no  effervescence.     It  crystallizes  from  95  per 
cent,    alcohol    in    prismatic    crystals.     Analysis    (Kjeldahl): 

Calculated  for 
C6H8N3C1.  Found. 

N  26.67  26.83 


2-Methylamino-5-methylpyrimidine,   CH3HNC         CCH3.  -- 

N  --  CH 

Five  grams  of  2-methylamino-5-methyl-6-chlorpyrimidine  and 
15  grams  of  zinc  dust  were  suspended  in  200  cc.  of  water  and 
the  mixture  digested  for  8  hours.  The  excess  of  zinc  was 
then  removed  by  nitration  and  the  filtrate  concentrated  on 
the  steam  bath.  We  obtained  a  thick  syrup  which  was  dissolved 
in  25  cc.  of  water  and  an  excess  of  a  saturated,  aqueous  solu- 
tion of  potassium  hydroxide  added.  A  light  colored  pre- 
cipitate was  formed  which  was  filtered  by  suction,  and  dried 
in  a  desiccator  over  sulphuric  acid. 

An  attempt  to  purify  this  substance  by  sublimation  was 
unsuccessful.  The  crude,  dry  material  was  finally  extracted 
several  times  with  boiling  ether.  When  the  excess  of  ether 
was  evaporated,  about  2  grams  of  a  colorless,  crystalline  sub- 
stance which  melted  at  97°-ioo°  to  a  clear  oil  was  obtained. 
In  order  to  purify  it  for  analysis  it  was  dissolved  in  dry 
ligroin  and  the  solution  allowed  to  concentrate  by  slow  evapora- 
tion. The  pyrimidine  separated  under  these  conditions  in 
beautiful,  transparent  prisms,  which  melted  sharply  at  102° 
to  a  clear  oil.  The  pyrimidine  is  extremely  soluble  in  cold 
water,  ether,  and  benzene.  It  showed  no  alkaline  reaction 
when  tested  with  turmeric  and  was  precipitated  from  an 
aqueous  solution  by  mercuric  chloride.  It  gave  at  first  no 
color  when  tested  with  diazobenzenesulphonic  acid,  but  on 
allowing  the  mixture  to  stand  a  strong  red  color  finally  de- 
veloped. The  pyrimidine  sublimes  when  heated  above  100°. 
Analysis  : 

Calculated  for 

C6H9N3.  Found. 

N  34.14  34.20 


Researches  on  Pyrimidines.  363 

An  attempt  was  made  to  reduce  the  6-chlorpyrimidine 
with  hydriodic  acid,  but  it  underwent  hydrolysis,  giving 
2-methylamino-5-methyl-6-oxypyrimidine. 

Picrate,  (C6H9N3)2.C0H3O7N3.—  This  salt  separated  imme- 
diately when  an  aqueous  solution  of  picric  acid  was  added 
to  a  solution  of  the  pyrimidine  base.  It  had  no  definite 
melting  point,  but  began  to  shrivel  at  about  100°  and  de- 
composed when  heated  above  150°.  Analysis: 

Calculated  for 
(C6H9N3)2.C6H307N8.  Found. 

N  26.53  26.36 

Hydrochloride,  (C6H9N3)2.HC1.H2O.—  This  salt  was  prepared 
by  dissolving  the  base  in  warm  hydrochloric  acid  and  con- 
centrating the  solution  on  the  steam  bath.  It  was  extremely 
soluble  in  water,  but  crystallized  from  methyl  alcohol  in  well- 
developed  prismatic  crystals.  The  salt  melts  at  i62°-i63° 
to  a  clear  oil  and  does  not  effervesce  below  250°.  Analysis: 

Calculated  for  Found. 

^CeHpNg.HCl. 

N 


26-33 

2i  .64 

.    (C8HgN3)2.HCl.H2O. 
27-95 

I.                    II. 
27.7          27.88 

NH—  CO 

2-Methylamino-4-methyl-6-oxy  pyrimidine,  CH3HNC         CH 

II          II 
N  -  CCH3 

—  We  prepared  this  pyrimidine1  by  heating  2-methylmer- 
capto-4-methyl-6-oxypyrimidine1  with  an  excess  of  methyl- 
amine  at  I4o°-i5o°.  The  yield  was  quantitative  and  the 
pyrimidine  melted  at  2Oi°-2O2°  after  one  recrystallization 
from  hot  water.  Analysis  (Kjeldahl)  : 

Calculated  for 

C«H9ON8.  Found. 

N  30.22  30.00 

2-Methylamino-4-methyl-6-chlorpyrimidinet 


CH.HNC         CH      .  —  Fourteen    and    five-tenths    grams  of 

II          II 
N  --  CCH, 

>  Loc.  citf 


364  Johnson  and  Mackenzie. 

2-methylamino-4-methyl-6-oxypyrimidine  and  72  cc.  of  phos- 
phorus oxychloride  were  heated  in  an  oil  bath  at  120°- 130° 
for  30  minutes,  when  the  evolution  of  hydrochloric  acid  gas 
had  practically  ceased.  We  obtained  a  clear  solution  which 
was  then  heated  at  100°  under  diminished  pressure  to  remove 
the  excess  of  phosphorus  oxychloride.  A  brown  oil  remained, 
which  was  dissolved  in  cold  water,  and  the  solution  made 
alkaline  with  sodium  hydroxide.  The  pyrimidine  separated 
in  colorless  crystals  and  was  dried  in  a  desiccator  over  sul- 
phuric acid.  It  is  very  insoluble  in  water  but  easily  soluble 
in  alcohol.  It  separates  from  an  alcohol  solution  in  long 
needles  which  melt  at  135°  to  a  yellow  oil  without  efferves- 
cence. It  slowly  sublimes  when  heated  above  100°.  Analysis 
(Kjeldahl) : 

Calculated  for 

C9H8N3C1.  Found. 

N  26.67  26.70 

Reduction  of  2-Methylamino-4-methyl-6-chlorpyrimidine  with 
Zinc. — This  chlorpyrimidine  is  very  slowly  reduced  by  di- 
gestion with  zinc  dust  because  of  the  insolubility  of  the  pyrimi- 
dine in  water.  Unaltered  chlorpyrimidine  was  recovered 
after  12  hours'  digestion  of  12  grams  of  the  pyrimidine  and 
50  grams  of  zinc  dust  in  1000  cc.  of  water.  One  hundred 
cc.  of  alcohol  were  then  added  and  the  mixture  boiled  again 
for  10  hours,  cooled  and  filtered.  By  extraction  of  the  zinc 
residue  with  alcohol,  we  recovered  6  grams  of  unaltered  6-chlor- 
pyrimidine.  The  aqueous  nitrate  was  concentrated  to  a 
volume  of  15-20  cc.  and  allowed  to  stand  at  ordinary  tem- 
perature, when  well-developed,  red  crystals  separated.  They 
melted  sharply  at  I7o°-i72°  to  an  oil  without  effervescence 
and  contained  zinc  and  chlorine.  The  substance  was  extremely 
soluble  in  water  and  did  not  lose  weight  when  heated  at  ioo°- 
110°.  A  nitrogen  determination  (Kjeldahl)  agreed  with  the 
calculated  value  for  a  double  compound  containing  3  mole- 
cules of  2-methylamino-4-methylpyrimidine  and  one  mole- 
cule of  zinc  chloride,  (C6H9N3)2.ZnCl2: 

Calculated  for 
(C»H9N,),ZnCl2.  Found. 

N  22.97  22.80 


Researches  on  Pyrimidines.  365 

The  filtrate  obtained  after  separation  of  the  zinc  chloride 
compound  was  concentrated  on  the  steam  bath  to  a  viscous 
liquid  and  then  triturated  with  about  25  cc.  of  a  strong,  aqueous 
solution  of  potassium  hydroxide.  An  amorphous  substance 
was  precipitated,  which  was  separated  by  suction  filtration, 
washed  with  a  few  drops  of  cold  water,  and  dried  in  a  desic- 
cator over  sulphuric  acid.  This  substance  was  then  extracted 
in  a  Soxhlet  apparatus  with  ether  for  three  days.  When 
the  ether  was  evaporated  we  obtained  an  oil  which  dissolved 
at  once  in  water,  alcohol  and  benzene.  In  order  to  estab- 
lish the  presence  of  2-methylamino-4-methylpyrimidine,  the 
oil  was  dissolved  in  water  and  a  solution  of  picric  acid  added 
to  the  aqueous  solution.  A  picrate  separated  at  once  in  the 
form  of  irregular  prisms  which  melted  at  I5o°-i55°  to  an 
oil  with  no  appreciable  effervescence.  This  salt  did  not  give 
a  test  for  chlorine.  Analysis  (Kjeldahl) : 

Calculated  for 
(C6H9N3)2.C6H807N3.     C6H9N3.C«H307Na.  Found. 

N  26.5  23.8  25.98 

2-Methylamino-4-methyl-6-chlorpyrimidine  was  converted 
into  2-methylamino-4-methyl-6-oxypyrimidine  when  heated 
with  hydriodic  acid. 

2-Ethylmercapto-4-carboxyl-5-methyl-6-oxypyrimidine, 
NH CO 

I  I 

C2H5S.C          CCHS     .  —  An  excellent  yield  of  this  pyrimidine 

II  II 

N CCOOH 

is  obtained  by  condensation  of  pseudoethylthiourea  with  the 
sodium  salt  of  diethyl  methyloxalacetate  in  aqueous  solution. 
In  our  preliminary  experiments  this  sodium  salt  was  pre- 
pared by  condensation  of  diethyloxalate  with  ethyl  propionate 
in  presence  of  sodium  ethylate.1  We  found,  however,  that 
the  use  of  dry  sodium  ethylate  is  unnecessary  and  that  as 
good  a  yield  of  the  salt  can  be  obtained  by  condensation  of 
the  esters  in  anhydrous  ether  in  presence  of  metallic  sodium. 
This  fact  is  shown  by  comparison  of  the  yields  of  pyrimidine 
given  in  the  table.  Our  method  of  preparing  the  pyrimidine 

i  Arnold:  Ann.  Chem.  (I^iebig),  246,  329. 


366  Johnson  and  Mackenzie. 

•  was  as  follows:  A  mixture  of  50  grams  of  ethyl  propionate 
and  7 1  grams  of  diethyl  oxalate  was  added  slowly  to  dry  ether, 
in  which  was  suspended  11.5  grams  of  metallic  sodium.  After 
the  esters  had  been  added  the  mixture  was  allowed  to  stand 
about  2  days  to  insure  a  complete  reaction.  Cold  water 
(about  500-600  cc.)  was  then  cautiously  added  to  dissolve 
the  sodium  salt,  and  the  ether  layer  separated.  To  this 
aqueous  solution  was  then  added  a  concentrated,  aqueous 
solution  of  52  grams  of  pseudoethylthiourea  hydrobromide 
and  finally  two  molecular  proportions  of  potassium  hydroxide 
(32  grams).  After  allowing  to  stand  for  2  days  at  4o°-5o° 
the  solution  was  concentrated  to  about  one-half  its  original 
volume,  cooled,  and  acidified  with  an  excess  of  strong  hydro- 
chloric acid.  The  pyrimidine  usually  separated  in  the  form 
of  a  light  pink  or  nearly  colorless,  granular  powder  melting 
at  2io°-2i5°  with  evolution  of  carbon  dioxide.  The  yield 
of  mercaptopyrimidine  is  decreased  by  using,  for  the  con- 
densation, more  than  two  molecular  proportions  of  potassium 
hydroxide  because  the  pyrimidine  is  slowly  converted  into 
thymine-4-carboxylic  acid,1  with  evolution  of  ethyl  mercaptan, 
when  warmed  with  strong  alkaline  solutions  (Experiment  5 
in  table). 

The  proportion  of  pseudoethylthiourea  hydrobromide  to 
be  used  for  a  condensation  was  calculated  upon  the  basis 
that  the  yield  of  sodium  salt  of  diethyl  oxalpropionate  is 
only  about  50  per  cent,  of  the  theoretical  (Arnold2  says  45 
percent.).  Under  these  conditions,  fifty  grams  of  ethyl 
propionate  require  for  condensation  45  grams  of  the  pseudo- 
thiourea  salt,  which  we  increased  to  52—54  grams  or  about 
0.6  molecular  proportion.  The  yield  of  pyrimidine  was  not 
increased  by  using  more  than  this  proportion  (see  Experiment 
2  in  table). 

1  Johnson:  J.  Biol.  Chem..  3,  299. 

2  Loc.  cit. 


Researches  on  Pyrimidines.  367 

Table  I. 


i 

o 

H 

I 

1 

^ 

I 

n 

W 

o 

5 

£C  CQ 

o 

0 

o^ 

fc 

JM 

M 

Grams. 

Grams. 

Grams. 

Grams. 

Grams. 

I 

50.0 

71.0 

"•5 

52.0 

16.0 

2 

50.0 

71.0 

ii.  5 

72.O 

22.  O 

3 

50.0 

71.0 

ii  .5 

54-o 

32-0 

4 

50-0 

71.0 

1  1  .  5  in  form 

54-0 

32.0 

NaOC2H5 

5 

IOO.O 

144.0 

22.5 

IOO.O 

108.0 

Ifil 

Grams. 
36.0 
36.5 

34-o 
37-0 

60.0  and  15.0 
(2 . 5  mols.)     of  thymine- 
4-carboxylic 

11.5  in  form  acid1 

6     50.0    71.0     NaOC2H5       45.0        30.0  22.0 

2-  Ethylmercapto-4-carboxyl  -  5  -  methyl-6-oxypyrimidine  is 
soluble  in  boiling  water  but  separates  on  cooling  in  clusters 
of  slender  needles  and  prismatic  crystals.  It  is  more  soluble 
in  alcohol  than  in  water.  It  decomposes,  after  crystalliza- 
tion from  water,  from  2i5°-2i8°  with  effervescence,  giving 
2-ethylmercapto-5-methyl-6-oxypyrimidine2  (see  below).  If 
the  acid  is  dissolved  in  dilute  sodium  hydroxide  solution 
and  reprecipitated  by  addition  of  hydrochloric  acid  it  sepa- 
rates in  colorless  crystals  melting  sharply  at  220°.  The  acid 
is  not  precipitated  from  aqueous  solutions  of  its  sodium  salt 
by  addition  of  acetic  acid. 

Analysis  (Kjeldahl) : 

Calculated  for  Found. 

C8HioO8NjtS.  I.  II. 

N  13.08  13.3  13.2 

Stability  of  the  Sodium  Salt  of  Diethyl  Oxalpropionate, 
C2H5OOC.C(ONa) :  C(CH3)COOC2H5.— Seventy-one  grams  of 
diethyl  oxalate  were  condensed  with  50  grams  of  ethyl  pro- 
pionate,  in  presence  of  sodium  ethylate,3  on  June  10,  1908. 
This  salt  was  then  allowed  to  stand  exposed  to  the  air,  in  an 

1  Johnson:  Loc.  cit. 

2  Loc.  cit. 

3  Arnold:  Loc.  cit. 


368  Johnson  and  Mackenzie. 

open  flask,  until  October  15,  1908.  It  was  then  condensed 
with  pseudoethylthiourea  in  the  usual  manner,  when  we 
obtained  22  grams  of  pyrimidine  melting  at  2O9°-2i4°  (Ex- 
periment 6  in  table). 

Ethyl  Ester  of  2-Ethylmercapto-4-carboxyl-5-methyl-6-oxypyr- 

NH— CO 
imidine, 

C2H5SC         CCH3          .—The  sodium  salt  of  diethyl 

II          II 

N CCOOC2H5 

oxalpropionate  was  prepared  in  the  usual  manner  by  con- 
densing 71  grams  of  diethyl  oxalate  with  50  grams  of  ethyl 
propionate  in  presence  of  metallic  sodium.  This  salt  was 
then  dissolved  in  400-500  cc.  of  water  and  mixed  with  an 
aqueous  solution  containing  0.6  molecular  proportion  of 
pseudoethylthiourea.  The  mixture  was  then  allowed  to 
stand,  at  ordinary  temperature,  for  several  days,  when  17.0 
grams  of  the  ethyl  ester  had  separated.  After  concentrating 
the  aqueous  filtrate  and  then  acidifying  with  hydrochloric 
acid,  we  obtained  the  corresponding  acid.  This  ester  is 
difficultly  soluble  in  water  but  very  soluble  in  boiling  alcohol. 
It  crystallizes  from  95  per  cent,  alcohol  in  prisms  which  melt 
at  i72°-i73°  to  a  clear  oil.  It  dissolves  in  sodium  hydroxide 
solution  without  decomposition  but  on  warming  it  easily 
undergoes  saponification.  The  ester  is  also  formed  quanti- 
tatively by  the  action  of  ethyl  iodide  on  the  silver  salt  of  2-ethyl- 
mercap to  -4-  carboxyl-5-methyl  -  6  -  oxy pyrimidine.  Analysis 
(Kjeldahl) : 

Calculated  for 

CioHi4O8N2S.  Found. 

N  11.56  ii. 8 

Behavior  of  2-Ethylmercapto-4-carboxyl-5-methyl- 6- oxy  pyr- 
imidine on  Heating. — A  few  grams  of  this  mercaptopyrimidine 
(3-4  grams)  were  heated  in  an  oil  bath  at  22o°-23o°  until 
effervescence  ceased.  A  dark  oil  was  obtained  which  solidified 
on  cooling.  This  substance  was  purified  by  crystallization 
from  hot  water  and  separated  in  prisms  melting  at  159°. 
It  was  identified  as  2-ethylmercapto-5-methyl-6-oxypyrimi- 
dine.1  Analysis  (Kjeldahl) : 

1  Wheeler  and  Johnson:  Loc.  cit. 


Researches  on  Pyrimidines.  369 

Calculated  for 
C7HioONjS.  Found. 

N  16.47  16.6 

Conversion  of  2-Eihylmercapto-4-carboxyl-5-methyl-6-oxypyr- 
imidine  into  Thymine. — Sixteen  grams  of  this  mercapto- 
pyrimidine,  melting  at  2i8°-22O°,  were  heated  in  an  oil  bath 
at  220°-230°  until  the  evolution  of  carbon  dioxide  ceased 
(about  1.5  hours).  We  obtained  13.0  grams  of  crude  2-ethyl- 
mercapto-5-methyl-6-oxypyrimidine  (theoretical  yield  is  12.7 
grams),  which  was  then  digested  for  several  hours  with  con- 
centrated hydrochloric  acid  and  converted  into  thymine. 
The  acid  solution  was  evaporated  to  dryness  and  the  crude 
thymine  decolorized  in  hot,  aqueous  solution  with  animal 
charcoal  and  then  crystallized  from  water.  It  separated 
in  colorless  crystals,  decomposing  at  about  325°-335°.  The 
yield  was  8.0  grams,  or  about  85  per  cent,  of  the  theoretical. 
Since  36-37  grams  of  2-ethylmercapto-4-carboxyl-5-methyl- 
6-oxypyrimidine  can  be  obtained  from  50  grams  of  ethyl 
propionate  (see  table)  this  amount  of  thymine  (8  grams) 
therefore  corresponds  to  21.6  grams  of  the  ester. 

A  quantitative  yield  of  thymine  from  21.6  grams  of  ethyl 
propionate  would  be  26.5  grams.  Analysis  (Kjeldahl) : 

Calculated  for 

C5H6OjN2.  Found. 

N  22.22  22.OO 

2-Methylamino-4-carboxyl-5-methyl-6-oxypyrimidine, 
NH— CO 

I  I 

CH3HNC         CCH3     .—Practically    a   quantitative   yield  of 

N CCOOH 

this  pyrimidine  was  obtained  when  7  grams  of  2-ethylmercapto- 
4-carboxyl-5-methyl-6-oxypyrimidine  and  9  grams  of  a  33 
per  cent,  solution  of  methylamine  were  heated  at  i4O°-i5o° 
for  4  hours.  It  was  precipitated  from  cold,  aqueous  solutions 
of  its  sodium,  ammonium  and  methylamine  salts  by  addition 
of  acetic  acid.  It  was  very  insoluble  in  cold  water  and  crys- 
tallized from  hot  water  in  long,  hairy  crystals  which  melted 


370  Johnson  and  Mackenzie. 

at  27O°-28o°,  according  to  the  rate  of  heating,  with  effervescence. 
Analysis  (Kjeldahl) : 

Calculated  for 
C7H9O8N8.  Found. 

N  22.9  22.4 

Methylamine  Salt,  C7H9O3N3.CH3NH2.— This  salt  crystal- 
lized from  hot  water  in  granular  crystals,  which  decomposed 
with  violent  effervescence  at  274°.  Two  of  the  crystals  that 
were  used  for  analysis  weighed  0.0393  and  0.03170  gram, 
respectively.  Analysis  (Kjeldahl) : 

Calculated  for 
C7H908N8.CH8NH2.  Found. 

N  26.1  25.91 

Hydrochloride,  C7H9O3N3.HC1.— This  salt  was  prepared  by 
dissolving  the  pyrimidine  base  in  hot,  dilute  hydrochloric 
acid  and  allowing  the  solution  to  cool.  The  salt  separated  in 
prismatic  crystals,  which  decomposed  at  276°-283°  with 
effervescence.  Analysis  (Kjeldahl) : 

Calculated  for 
CjHsOaNa.HCl.  Found. 

N  I9-I4  I9-32 

NEW  HAVEN,  CONN., 
June  1,  1909. 


[Reprinted  from  The  American  Chemical  Journal, 
Vol.  XI.II.    No.  5.    November,  1909.] 


[Contributions  from  the  Sheffield  Laboratory  of  Yale  University.] 

CLXXIL— RESBARCHKvS  ON  PYRIMIDINES: 

THE  ACTION  OF  METHYL  IODIDE  AND  OF  BENZYL 

CHLORIDE  UPON  2-OXY-4-METHYL-6-METHYL- 

MERCAPTOPYRIMIDINE.2 

[FORTY-SEVENTH  PAPER.  ] 

BY  HENRY  L.  WHEELER  AND  DAVID  F.  MCFARLAND. 

The  papers  so  far  published  on  the  alkylation  of  mercapto- 
pyrimidines,  with  but  one  exception,  have  been  confined  to 
a  description  of  the  results  obtained  from  a  study  of  2-mer- 

2  Part  of  a  thesis  presented  by  David  F.  McFarland  for  the  degree  of  Ph.D.,  Yale, 
1909. 


432  Wheeler  and  McFarland. 

capto-6-oxypyrimidines.  In  most  cases  2-mercapto-6-oxy- 
pyrimidines  were  found  to  alkylate  both  in  the  i-  and,  more  or 
less,  in  the  3-position.1 

In  the  exception  mentioned,  Wheeler  and  Johnson2  showed 
that  when  a  compound  having  the  opposite  configuration, 
the  me  reap  to  group  and  the  oxygen  atom  being  interchanged, 
2-oxy-6-methylmercaptopyrimidine  for  example,  was  treated 
with  potassium  hydroxide  and  either  methyl  iodide  or  benzyl 
chloride,  3-alkyl  derivatives  were  obtained.  No  i -derivative 
was  observed  in  this  particular  alkylation.  Since  the  3-alkyl- 
6-mercapto  derivatives  pass  quantitatively  into  the  3-alkyl 
compounds  of  uracil  when  boiled  with  hydrochloric  acid, 
this  procedure  is  therefore  the  best  for  the  preparation  of 
these  compounds. 

With  this  result  at  hand,  it  then  became  a  question  whether 
or  not  2-oxy-6-mercaptopyrimidines  in  other  cases  or  in 
general  would  be  the  best  to  select  for  the  preparation  of 
3-alkyl  derivatives.  Cytosine,  or  2-oxy-6-aminopyrimidine, 
which  has  a  constitution  analogous  to  these  2-oxy-6-mercapto- 
pyrimidines,  also  gives  the  3-alkyl  derivative  on  methylation.3 

It  seems  to  us  that  any  new  facts  in  regard  to  methods 
which  lead  to  the  formation  of  3-alkyl  derivatives  or  3-attach- 
ments  are  of  interest  since  results  have  been  obtained  by 
Johnson  and  Clapp4  which  can  be  explained  by  the  assump- 
tion that  uracil,  thymine,  and  cytosine  are  substituted  or 
attached  to  other  groups  in  these  positions  in  the  nucleic 
acids. 

In  our  preceding  paper  we  have  shown  that  2-methylmer- 
capto-  and  2-ethylmercapto-4-methyl-6-oxypyrimidine  give 
i-alkyl  derivatives,  the  formation  of  the  isomeric  3-deriva- 
tives  in  these  cases  not  being  observed.  It  was  there- 
fore of  especial  interest,  in  the  above  connection,  to  study,  in 
this  case,  the  alkylation  of  the  compound  having  the  opposite 
configuration,  namely,  2-oxy-4-methyl-6-methylmercapto- 

1  For  a  list  of  these  papers  see  THIS  JOURNAL,  42,  30  (1909). 

2  Ibid. 

3  Johnson  and  Clapp:  J.  Biol.  Chem.,  5,  163  (1908). 

4  Loc.  cit. 


Researches  on  Pyrimidines.  433 

pyrimidine.  This  has  now  been  done  and  we  find  that  this 
pyrimidine,  with  methyl  iodide  and  benzyl  chloride,  not  only 
gives  3-alkyl  derivatives  but  also  the  isomeric  i -compounds. 
In  the  case  of  the  action  of  methyl  iodide,  the  i-  and  3-iso- 
mers  are  formed  in  about  equal  proportions.  Benzyl  chloride 
gave  more  of  the  3-  than  of  the  i -benzyl  compound. 

The  presence  of  a  mercapto  group  or  the  absence  of  oxygen 
in  the  6-position  therefore  appears  to  favor  the  formation  of 
3-alkyl  derivatives.  There  is,  however,  no  strict  regularity 
in  these  alkylations,  so  that  in  new  cases  it  is  impossible  to 
predict  whether  a  i-  or  3-derivative,  or  a  mixture  of  both, 
will  result. 

The  starting  point  for  the  present  work  was  the  prepara- 
tion of  List's1  2-thio-4-methyluracil  (I)  from  acetoacetic 
ester  and  thiourea.  This  gave  2-methylmercapto-4-methyl- 
6-oxypyrimidine  (II)  by  List's  method  of  alkylation. 

The       new       2-methylmercapto-4-methyl-6-chlorpyrimidine 

(III)  was  then  prepared  by  warming    the  material  with  phos- 
phorus   pentachloride    and    some    oxychloride.     When    this 
compound  was  warmed  with  an  excess  of  alcoholic  potassium 
sulphhydrate,        2-methylmercapto-4-methyl-6-thiopyrimidine 

(IV)  was   obtained,    and    when   the   latter   was   boiled   with 
hydrochloric  acid  4-methyl-6-thiouracil  (V)  resulted. 

The  calculated  quantity  of  sodium  ethylate  and  methyl 
iodide  then  gave  2-oxy-4-methyl-6-methylmercaptopyrimi- 
dine  (VI).  An  excess  of  potassium  hydroxide  and  methyl 
iodide,  in  alcoholic  solution,  gave  2-oxy-3,4-dimethyl-6- 
methylmercaptopyrirnidine  (VIII)  and  2-oxy-i,4-dimethyl- 
6-methylmercaptopyrimidine(?)  (VII).  The  latter  was  not 
obtained  in  a  state  of  purity  but  its  presence  in  the  oily 
fraction  was  indicated  by  the  behavior  of  this  fraction 
toward  hydrochloric  acid.  When  boiled  with  hydrochloric 
acid  the  compounds  VII  and  VIII  gave  the  correspond- 
ing dimethyluracils  described  by  Behrend,2  namely,  i,4-di- 
methyluracil  (IX)  and  3,4-dimethyluracil  (X). 

1  Ann.  Chem.  (Liebig),  236,  12  (1886). 

2  Behrend  and  Dietrich:  Ann.  Chem.    (Liebig),  309,  265    (1899).     Behrend  and 
Thurn:  Ibid.,  323,  160  (1902). 


434  Wheeler  and  McFarland. 

The  formation  of  i-alkyl  derivatives  in  this  reaction  could 
be  explained  otherwise,  without  the  assumption  of  the  forma- 
tion of  the  compound  represented  by  formula  VII,  if  2-0x7-4- 
methyl-6-methylmercaptopyrimidine  lost  mercaptan  during 
the  alkylation.  4-Methyluracil  being  formed,  i-alkyl  de- 
rivatives would  result.  However,  we  have  treated  2-oxy-4- 
methyl-6-methylmercaptopyrimidine  with  alkali,  under  the 
same  conditions  as  those  in  the  alkylations,  and  we  have 
found  that  no  4-methyluracil  was  formed.  The  mercapto 
compound  was  recovered  unaltered.  The  various  steps  in 
the  synthesis  of  these  pyrimidines  may,  therefore,  be  repre- 
sented as  follows : 


N==< 


N CCH3 

IV. 


CH3N CO 

:H 


oc      a 


CH3N CCH3  N=CCH3  HN CCH3 

VIII.  VII.  IX. 


Researches  on  Pyrimidines.  435 


PART. 

2-Methylmercapto-4-methyl-6-chlorpyrimid'ine, 
N===CC1 


[3SC        CH  .— Fi 


CH3SC         CH  .  —  Fifty      grams     of     2  -  methylmercapto  -  4  - 

II          II 
N  --  CCH3 

methyl-6-oxypyrimidine  were  moistened  with  phosphorus 
oxychloride  in  a  distilling  bulb  and  then  one  molecular  pro- 
portion (66.8  grams)  of  phosphorus  pentachloride  was  added. 
No  action  was  observed  in  the  cold,  and  even  when  the  mix- 
ture was  warmed  the  reaction  began  only  very  slowly.  The 
mass  slowly  liquefied  with  a  regular,  quiet  evolution  of  hydro- 
gen chloride.  After  two  hours  warming,  the  liquefaction 
was  complete  and  the  evolution  of  gas  was  greatly  diminished. 
The  phosphorus  oxychloride  was  removed  by  distilling  under 
reduced  pressure,  and  the  oil  which  remained  was  poured  on 
cracked  ice.  It  solidified  to  a  yellow  solid,  which  was  allowed 
to  remain  in  the  ice  water  for  some  time  and  then  extracted 
with  ether.  The  solution  was  dried  with  calcium  chloride 
and,  on  evaporation,  the  oil  obtained  was  distilled  at  32-35 
mm.  pressure.  The  greater  part  (42  .  8  grams)  boiled  steadily 
at  147°.  This  is  77  per  cent,  of  the  calculated.  On  cooling, 
this  fraction  solidified  and  then  melted  at  39°-4O°.  The 
substance  is  very  soluble  in  all  of  the  common  solvents.  When 
dissolved  in  the  smallest  possible  quantity  of  petroleum  ether 
it  separated  in  beautiful,  long  needles.  These  were  pressed 
on  filter  paper  and  dried  in  a  desiccator  for  analysis: 

Calculated  for 


Found. 

N  16.02  16.02 

2-Methylmercapto-4-methyl-6-thiopyrimidine, 
HN  -  CS 


[3SC 


CH3SC         CH  . — Ten  grams   of   the   above    chlorpyrimidine 

II          II 
N CCH3 

were  mixed  with  an  alcoholic  solution  of  potassium  hydro- 
sulphide,  made  by  saturating  a  solution  of  19.2  grams  of  potas- 


436  Wheeler  and  McFarland. 

slum  hydroxide  in  60  cc.  of  alcohol  with  hydrogen  sulphide. 
The  chlor  compound  dissolved  and  very  soon  crystals  of  the 
potassium  salt  of  2-methylmercapto-4-methyl-6-thiopy- 
rimidine  began  to  separate.  The  mixture  was  warmed  for 
half  an  hour  on  the  steam  bath  and  the  alcohol  was  then 
evaporated.  The  residue  dissolved  almost  completely  in 
water  and  the  solution  was  filtered  from  a  slight  reddish  sedi- 
ment. On  acidifying  with  dilute  acetic  acid,  the  free  thio 
compound  was  precipitated.  The  quantity  obtained  (9.85 
grams)  agreed  almost  exactly  with  the  theoretical  yield. 
This  substance  is  very  difficultly  soluble  in  boiling  water, 
from  which  it  separates  in  light  yellow,  minute  needles.  It 
dissolves  easily  in  ammonium  hydroxide  and  separates  again 
when  the  ammonia  is  boiled  off.  It  is  unstable  in  aqueous 
alkali  and  the  solution  takes  on  a  dark  red  color.  Dilute 
alcohol  or  water  should  therefore  not  be  used  in  its  prepara- 
tion. Alcohol  dissolves  it  with  some  difficulty,  giving  needle- 
like  prisms.  On  standing,  the  alcoholic  mother  liquors  take 
on  a  deep  red  color. 

Calculated  for 

C6H8N2S2.  Found. 

N  16.27  16.12 

2-Methylmercapto-4-methyl-6-thiopyrimidine  exhibited  a 
characteristic  behavior  when  heated,  the  product  obtained 
at  high  temperatures  being  2,6-dithio-4-methyluracil.  This 
substance  has  been  described  by  Gabriel  and  Colman.1  When 
slowly  heated,  such  as  is  commonly  done  in  taking  melting 
points,  it  partially  melted,  like  a  mixture,  at  212°  to  a  milky 
mass,  which  effervesced  on  further  heating  and  then  solidified. 
If  the  tube  was  placed  in  a  bath  already  heated  to  200°  and 
the  temperature  rapidly  raised,  it  then  melted  completely 
to  a  clear  yellow  oil  at  214°.  A  slight  elevation  of  tempera- 
ture caused  the  oil  to  effervesce  and  finally  solidify  to  a  crys- 
talline solid.  On  further  heating  this  solid  grew  red,  the 
color  deepening  until  the  material  melted  or  decomposed  to  a 
red-brown  oil  at  28o°-29O°. 

One  gram  of  the  mercapto-6-thiopyrimidine  was  heated  for 

1  Ber.  d.  chem.  Ges.,  32,  2921  (1899). 


Researches  on  Pyrimidines.  437 

a  short  time  at  2i5°-223°.  The  product  was  treated  with 
hot  alcohol  and  the  portion  which  did  not  dissolve  was  found 
to  be  also  almost  insoluble  in  boiling  water.  On  heating, 
decomposition  set  in  above  260°,  but  the  material  did  not  melt 
at  310°.  A  nitrogen  determination  gave  17.53  Per  cent. 
while  the  calculated  for  2,6-dithio-4-methyluracil  is  17.72 
per  cent. 

HN  --  CS 

6-Thio-4-methyluracil,  OC         CH     .  —  This     compound    is 

I  II 

HN  -  CCH3 

formed  quantitatively  by  boiling  2-methylmercapto-4-methyl- 
6-thiopyrimidine  with  strong  hydrochloric  acid  for  several 
hours  and  then  evaporating  to  dryness.  Long  heating  is  re- 
quired to  completely  expel  the  mercaptan  from  the  com- 
pound. The  product  is  almost  insoluble  in  alcohol  and  diffi- 
cultly soluble  in  boiling  water.  It  crystallizes  in  irregular, 
prismatic  forms,  has  a  sulphur-yellow  color,  but  no  definite 
melting  point.  When  heated  it  decomposes  above  250°. 

Calculated  for 


Found. 
N  19-71  !9-42 

The  sulphur  in  this  compound  is  more  firmly  bound  than 
that  in  6-thiouracil  or  6-thiothymine.  It  was  not  removed 
on  long  heating  on  the  steam  bath  with  hydrochloric  acid. 

2-Oxy-4-methyl-6-methylmercaptopyrimidine, 


OC          CH      .  —  Seven   and    six-tenths    grams    of    6-thio-4- 

I  II 

HN  -  CCH5 

methyluracil  were  dissolved  by  warming  with  2.2  grams  of 
sodium  hydroxide  in  50  cc.  of  water  and  30  cc.  of  methyl 
alcohol,  and  8.5  grams  of  methyl  iodide  were  added.  The 
mixture  was  warmed  until  no  further  alkaline  reaction  was 
obtained.  It  was  then  evaporated  to  dryness.  The  product 
dissolved  easily  in  water,  leaving  only  a  little  oil,  which  was 
removed  by  filtration.  On  standing,  pale  yellow,  flat,  needle- 


438  Wheeler  and  McFarland. 

like  crystals  formed.  The  yield  in  one  case  was  83  per  cent. 
of  the  calculated.  When  recrystallized  from  water  the  ma- 
terial melted  at  i74°-i75°  to  a  clear  oil.  The  substance 
was  very  soluble  in  water  and  alcohol,  and  it  had  a  tendency 
to  form  supersaturated  solutions.  On  this  account  it  crys- 
tallized from  water  only  after  standing  for  some  time.  It 
is  not  appreciably  volatile  with  steam. 

Calculated  for 

Found. 


N  17.94  17-67 

Action  of  Benzyl  Chloride.  —  Four  grams  of  2-oxy-4-methyl- 
6-methylmercaptopyrimidine  were  dissolved  in  alcohol  with 
1.45  grams  of  potassium  hydroxide.  To  the  cooled  solution, 
3  .  3  grams  of  freshly  distilled  benzyl  chloride  were  added  and 
the  mixture  was  allowed  to  stand  for  several  days.  The  re- 
action then  still  being  incomplete,  the  mixture  was  warmed 
for  two  hours  on  the  steam  bath.  Some  potassium  chloride 
which  separated  was  filtered  off  and  the  solution  was  allowed 
to  evaporate  spontaneously.  A  small  amount  of  solid  re- 
mained, mixed  with  a  larger  quantity  of  red  oil,  which  had  a 
very  pungent  odor.  When  the  mixture  was  spread  on  a  porous 
plate  the  oil  was  absorbed,  leaving  i  .  6  grams  of  the  sticky 
solid.  This  was  very  soluble  in  alcohol  and  benzene  and  very 
difficultly  soluble  in  water.  From  none  of  these  solutions  could  a 
pure  crystalline  substance  be  obtained,  so  the  crude  solid  was 
treated  directly  with  hydrochloric  acid. 

One  and  a  half  grams  of  the  solid  were  digested  on  the  steam 
bath  with  a  large  excess  of  concentrated  hydrochloric  acid 
and  then  evaporated  to  dryness.  This  operation  was  twice 
repeated  before  mercaptan  was  completely  eliminated.  The 
residue  weighed  i  .  i  grams.  On  crystallizing  from  alcohol 
it  was  found  to  consist  principally  of  4-methyluracil,  decom- 
posing at  265°-3oo°,  and,  by  extracting  the  product  with 
cold  chloroform  a  very  small  amount  of  i  -benzyl-  4-methyl- 
uracil was  obtained.  The  red  oil,  which  was  absorbed  in  a 
porous  plate,  was  extracted  with  boiling  alcohol  and  treated 
with  concentrated  hydrochloric  acid  as  above.  When  mer- 


Researches  on  Pyrimidines.  439 

captan  ceased  being  evolved,  the  dry  residue  was  stirred  with 
alcohol.  This  left  i .  i  grams  of  substance  undissolved,  while 
the  red  color  of  the  residue  was  removed.  When  the  ma- 
terial was  crystallized  once  from  alcohol,  Hagen's  j-benzyl-4- 
methyluracil,  melting  at  2^i°-2^2°,  was  obtained.  The  mother 
liquor  appeared  to  contain  a  mixture  of  this  compound  and  of 
the  i -benzyl  derivative.  We  conclude  from  the  above  that  of  the 
two  isomers  the  3-benzyl  derivative  is  formed  in  larger  amount. 

Action  of  Methyl  Iodide',  2-Oxy-3,4-dimethyl-6-methylmer- 
captopyrimidine. — Four  and  three- tenths  grams  of  potassium 
hydroxide  were  dissolved  in  50  cc.  of  methyl  alcohol  and  4 
grams  of  2-oxy-4-methyl-6-methylmercaptopyrimidine  were 
added.  This  dissolved  at  once  without  warming.  Three 
molecular  proportions  (n  grams)  of  methyl  iodide  were  then 
added  and  the  mixture  was  allowed  to  stand  two  days.  At 
the  end  of  this  time  considerable  potassium  iodide  had  sepa- 
rated and  the  solution  no  longer  gave  an  alkaline  reaction. 
The  alcohol  was  then  evaporated  under  reduced  pressure 
and  the  dry  residue  was  extracted  with  three  portions  of  boil- 
ing chloroform.  On  evaporation  of  the  chloroform  at  ordi- 
nary temperatures,  slightly  yellow,  large,  prismatic  crystals 
mixed  with  oil  separated.  The  oil  did  not  solidify  on  stand- 
ing for  some  time.  It  was  removed  by  absorption  in  filter 
paper  and  saved  for  later  treatment  (see  below). 

The  crystals,  which  weighed  2 . 3  grams  or  53  per  cent,  of  the 
calculated  for  dimethyl-6-methylmercaptopyrimidine,  were 
twice  recrystallized  from  benzene.  Some  brownish  color  was 
removed  by  boiling  the  solution  with  animal  charcoal,  where- 
upon, on  filtering,  splendid  prisms,  somewhat  irregular  in 
outline,  were  obtained.  They  melted  to  a  clear  oil  at  170°- 
171°,  and  were  found  to  be  very  soluble  in  water  and  in  alco- 
hol, but  only  moderately  so  in  benzene. 

Calculated  for 
CyHioONjjS.  Found. 

N  16.47  16.53 

This  material  was  boiled  with  hydrochloric  acid  until  it 
gave  no  test  for  sulphur.  It  was  then  crystallized  twice  from 
alcohol,  whereupon  it  melted  at  220°  and  agreed  in  proper- 


440  Wheeler  and  McFarland. 

ties  with  Behrend's  3,4-dimethyluracil.  A  nitrogen  deter- 
mination gave  20.06  per  cent,  nitrogen  while  the  calculated 
for  this  compound  is  20  .  oo  per  cent. 

1,4-  Dimethyl  -  2  -  oxy-6-mefhylmercaptopyrimidine  (?).  —  This 
compound  was  not  isolated  in  a  pure  state  but  its  presence 
in  the  oil  obtained  above  was  indicated  by  the  hydrolysis  of 
the  oil  with  strong  hydrochloric  acid.  After  digesting  on  the 
steam  bath  until  mercaptan  was  no  longer  evolved,  the  solu- 
tion was  evaporated  to  dryness  and  the  residue  was  crystal- 
lized from  water.  It  separated  in  small  prisms  melting  sharply, 
to  a  clear  brown  oil,  at  260°  and  when  mixed  with  a  sample 
of  /?-dimethyluracil  or  i,4-dimethyluracil  the  melting  point 
was  not  lowered. 

Calculated  for 
C6H8O2N2.  Found. 

N  20  .  00  20  .  02 

2  -  Oxy  -4-  methyl  -  6  -  orthonitrobenzylmercaptopyrimidine.  — 
Molecular  proportions  of  6-thio-4-methyluracil,  potassium 
hydroxide,  and  o-nitrobenzyl  chloride  were  mixed  in  dilute 
alcoholic  solution.  The  mixture  was  then  warmed  until  it 
gave  a  neutral  reaction.  When  the  alcohol  was  evaporated 
and  the  residue  was  treated  with  water  the  yield  of  crude 
product  agreed  with  the  calculated  amount.  This  material 
dissolved  fairly  easily  in  hot  alcohol  and,  on  cooling,  it  gave 
clusters  of  yellow,  lancet-shaped  crystals  melting  to  a  clear 
oil  at  205°. 

Calculated  for 

Found. 


N  15.16  15.24 

2  -  Oxy  -  4  -  methyl  -  6  -  metadinitrophenylmercaptopyrimi- 
dine,  prepared  in  a  similar  manner  to  the  above,  from  6-thio- 
4-methyluracil,  potassium  hydroxide,  and  i-brom-2,4-dinitro- 
benzene,  formed  very  small  bunches  of  fine,  mustard-yellow 
needles  when  crystallized  from  alcohol.  It  melted  at  208°. 

Calculated  for 
CiiH806N4S.  Found. 

N  18.18  18.05 

NEW  HAVEN,  CONN., 
May,  1909. 


[Reprinted  from  The  American  Chemical  Journal, 
Vol.  XLII.    No.  6.    December,  1909.] 


[Contributions  from  the  Sheffield  Laboratory  of  Yale  University.] 

CLXXV.— RESEARCHES  ON  PYRIMIDINES: 

SYNTHESIS  OF  5-CYANURACIL. 

[FORTY-EIGHTH  PAPER.] 

BY  TREAT  B.  JOHNSON. 

The  present  work  was  undertaken  with  the  object  of  pre- 
paring some  pyrimidines  to  be  used  for  the  syntheses  of  new 


506  Johnson. 

derivatives  of  thymine.  I  shall  describe  the  preparation  and 
properties  of  the  nitrile  of  uracil-5-carboxylic  acid  (I),  viz., 
5-cyanuracil  (II),  and  some  of  its  derivatives. 

NH— CO  NH— CO 

I  I  II 

CO     CCOOH  CO     CCN 

I          II  I         II 

NH— CH  NH— CH 

(I)  (II) 

It  has  been  shown  in  a  previous  paper  from  this  laboratory1 
that  diethyl  ethoxymethylenemalonate,2 

C2H5OCH  :  C(COOC2H5)2, 

condenses  smoothly  with  pseudothioureas,  H2NC(SR)  :  NH, 
in  aqueous  solution,  in  the  presence  of  alkali,  giving  2-alkyl- 
mercapto-5-carboxyl-6-oxypyrimidines.  Uracil  -  5  -  carboxylic 
acid  (I)  is  then  obtained  easily  by  hydrolysis  of  these  mer- 
captopyrimidines  with  acids.  It  seemed  very  probable  to 
the  writer  that  5-cyanuracil  (II)  might  be  synthesized  in  an 
analogous  manner  from  ethyl  ethoxymethylenecyanacetate, 

C2H5OCH  :  C(CN)COOC2H5. 

DeBollemont3  has  described  several  esters  of  this  character, 
which  he  has  prepared  by  condensation  of  orthoformic  esters, 
CH(OR)3,  with  esters  of  cyanacetic  acid  in  presence  of  acetic 
anhydride.  He  has  also  examined  the  behavior  of  several  of 
them  towards  organic  bases  and  shown  that  they  react  smoothly 
with  formation  of  the  corresponding  amino  derivatives, 

RHNCH  :  C(CN)COOR. 

The  action  of  ureas,  thioureas,  pseudoureas,  and  pseudo- 
thioureas on  these  esters,  however,  has  not  been  investigated. 
Ethyl  ethoxymethylenecyanacetate  was  prepared  for  my 
experiments  according  to  the  directions  of  deBollemont.4  I 
now  find  that  pseudoethylthiourea  condenses  in  alcoholic 

1  THIS  JOURNAL,  37,  392  (1907).  ( 

2  Claisen:  Ann.  Chem.  (Liebig),  297,  75  (1897). 

3  Compt.  Rend.,  128,  1338;  129,  5;  Bull.  Soc.  Chim.,  [3]  25,  18,  28,  39. 

4  Loc.  cit. 


Researches  on  Pyrimidines.  507 

solution  with  this  ester,  in  the  presence  of  alkali,  in  two  ways, 
giving  a  mixture  of  two  mercaptopyrimidines.  The  main 
reaction  is  a  condensation  with  the  ester,  similar  to  that 
with  diethyl  ethoxymethylenemalonate,1  giving  2-ethyl- 
mercapto-5-cyan-6-oxypyrimidine  (III).  This  condensation 
is  represented  by  the  following  equation: 

NH2     COOC2H5  NH— CO 

II  II 

C2H5SC    +    CCN  =   2C2H5OH  +  C2H5SC        CCN 

II  II  II         II 

NH      CHOC2H5  N CH 

(III) 

A  part  of  the  acrylic  ester,  however,  reacts  with  the  pseudo- 
thiourea,  giving  2-ethylmercapto-5-carbethoxy-6-amino- 
pyrimidine  (IV),  which  has  previously  been  described  in  a 
paper  from  this  laboratory.2 

NH2        CN  N  =  CNH2 

II  II 

C2H5SC     +     CCOOC2H5  =  C2H5OH  +  C2H5SC  =  CCOOC2H5 

II  II  ||      II 

NH        CHOC2H5  N— CH 

(IV) 

This  interesting  observation  suggests  that  other  cyanides 
containing  the  grouping  C2H5OCH  :  C  —  CN  will  be  found  to 

I 

condense  with  pseudothioureas,  giving  aminopyrimidines. 
It  is  interesting  to  note  here  that  ethyl  acetylcyanacetate, 

CH3COCH(CN)COOC2H5, 

does  not  condense  with  pseudoethylthiourea  to  give  a 
pyrimidine.3  On  the  other  hand,  it  has  been  shown  that  the 
pseudoureas,4  H2NC(OR)  :  NH,  condense  with  ethyl  cyan- 
acetate,  in  presence  of  alkali,  giving  the  corresponding  2-alkyl- 
oxy-4-amino-6-oxypyrimidines.5 

1  Loc.  cit. 

2  Wheeler  and  Johns:  THIS  JOURNAL,  38,  594. 

3  Wheeler:  THIS  JOURNAL,  28,  358. 

4  Stieglitz  and  McKee:   Ber.  d.  chem.  Ges.,  32,  1494;  33,  807,  1517;  Stieglitz  and 
Noble:  Ibid.,  38,  2243. 

"Central.,  1904,11,   631. 


508  Johnson. 

I  also  investigated  the  action  of  pseudoethylthiourea  on  ethyl 
ethoxymethylenecyanacetate  (V)  in  alcohol  containing  no  free 
alkali.  When  they  were  allowed  to  react  under  these  conditions 
in  molecular  proportions,  there  was  no  evidence  of  the  forma- 
tion of  2-ethylmercapto-5-cyan-6-oxypyrimidine  (III),  and 
2-ethylmercapto-5-carbethoxy-6-aminopyrimidine  (IV)  and 
ethyl  a-cyan-/?-pseudoethylthiourea-acrylate  (VIII)  were  the 
only  products  of  the  reaction.  If  more  than  one  molecular 
proportion  of  pseudoethylthiourea  is  used  for  the  condensation 
the  ethyl  a-cyan-/?-pseudoethylthiourea-acrylate  that  is  formed 
then  reacts  with  the  excess  of  pseudothiourea,  giving  a-cyan-/?- 
pseudoethylthiourea-acrylpseudoethylthiourea  (VI) . 

Ethyl  a-cyan-/?-pseudoethylthiourea-acrylate  (VIII)  and 
a-cyan-/?-pseudoethylthiourea-acrylpseudoethylthiourea  (VI) 
are  both  converted  quantitatively  into  2-ethylmercapto-5- 
cyan-6-oxypyrimidine  (III)  when  warmed  with  alkali.  A 
quantitative  yield  of  5-cyanuracil  (XI)  is  then  obtained  by 
hydrolysis  of  this  mercaptopyrimidine,  in  alcohol,  with  sul- 
phuric acid.  Attempts  to  hydrolyze  this  mercaptopyrimidine 
(III)  smoothly  to  5-cyanuracil,  in  aqueous  solution,  were 
unsuccessful.  The  nitrile  group  slowly  undergoes  hydrolysis 
under  these  conditions,  giving  a  mixture  of  5-cyanuracil  (XI) 
and  uracil-5-carboxamide  (X).  These  are  both  converted 
quantitatively  into  uracil-5-carboxylic  acid  (IX)  and  finally  into 
uracil  (VII)  by  long  digestion  with  concentrated  hydrochloric 
acid.  These  various  transformations  are  represented  by  the 
following  formulas : 


Researches  on  Pyrimidines. 


509 


O 


3—  o— 

tti     O 


O— 

o 


HL04~*HLQ_ 


8 

O 

w 


5—0—3 


P 
JU 

2=0—  szj 


W 


0=0—0 


o 


o  — 
W 

O—  0 

o     o 

o 

1 

0= 

w 

1 

8^ 

%      r 

<  *—  <  O 

O 

I             « 
/             »• 

i 

^ 

o 


\ 


^—  o—  * 
W     °     W 

M   I 

M  i 

~ 


p 

w 


0=0—0 
Wgo 


W 


0=0—0 
W     o     o 


ffi 

o 

P 
W 


o 


a; 

W 


5  io  Johnson. 

EXPERIMENTAL   PART. 

Ethyl  Ethoxymethylenecyanacetate, 

C2H5OCH  :  C(CN)COOC2H5.—  This  ester  was  prepared  ac- 
cording to  the  directions  given  by  de  Bollemont.1  It  melts  at 
52°~53°  anc*  is  insoluble  in  water  but  very  soluble  in  alcohol, 
ether,  and  benzene. 

Condensation    of    Ethyl    Ethoxymethylenecyanacetate    with    One 
Molecular   Proportion   of   Pseudoethylthiourea   in   Alcohol. 

Ethyl  a-Cyan-fl-pseudoethylthiourea-acrylate, 
NH2     COOC2H5 

C2H5SC          CCN         .  —  Molecular  proportions   of  potassium 

N-—  CH 

hydroxide  (0.45  gram)  and  the  hydrobromide  of  pseudoethyl- 
thiourea  (1.4  grams)  were  dissolved  separately  in  7  cc.  of 
95  per  cent,  alcohol,  the  solutions  cooled  to  o°,  and  combined. 
The  undissolved  potassium  bromide  was  then  separated 
quickly  by  filtration  and  1.2  grams  of  ethyl  ethoxymethylene- 
cyanacetate  added  to  the  cold  alcohol  solution  of  pseudo- 
thiourea.  The  ester  dissolved  at  once  and  within  1-2  minutes 
a  yellow,  crystalline  substance  separated.  After  standing  a 
few  minutes  this  was  filtered  off,  washed  thoroughly  with 
ether,  and  the  ether  washings  saved  (see  below).  The  sub- 
stance obtained  here,  insoluble  in  ether,  was  the  ethyl  acrylate 
represented  above  and  melted  without  further  purification  at 
I2o°-i25°.  The  ester  is  soluble  in  alcohol,  insoluble  in  cold 
water  and  ether,  and  crystallizes  from  benzene  in  tufts  of  yel- 
low distorted  needles  melting  at  130°  with  slight  effervescence. 
It  separates  from  a  hot  aqueous  solution  as  an  oil,  which 
finally  crystallizes  in  colorless  needles  melting  at  the  same 
temperature.  Nitrogen  (Kjeldahl)  : 

Calculated  for 

Found. 


N  18.50  18.7 

Loc.  cit. 


Researches  on  Pyrimidines.  511 

2-Ethylmercapto-5-carbethoxy-6-aminopyrimidine, 
N  =  CNH2 

I  I 

C2H5SC     CCOOC2Hto.— This  pyrimidine  was    obtained    when 

II  II 
N— CH 

the  ether  solution  described  above  was  allowed  to  evaporate. 
It  was  insoluble  in  cold,  dilute  sodium  hydroxide  solution 
but  soluble  in  hydrochloric  acid,  and  crystallized  from  95  per 
cent,  alcohol  in  rectangular  plates  melting  at  iO2°-iO3°  to  a 
clear  oil  with  no  effervescence.  This  same  pyrimidine  has 
previously  been  described  by  Wheeler  and  Johns.1  A  mixture 
of  my  derivative  and  their  pyrimidine  melted  at  102°.  Ni- 
trogen (Kjeldahl) : 

Calculated  for 
C»H,302N3S.  Found. 

N  18.50  18.6 

The  comparative  yields  of  the  above  acrylic  ester  and  this 
6-aminopyrimidine  were  irregular,  but  the  ester  was  always 
the  chief  product  of  the  reaction.  They  were  apparently 
the  only  compounds  formed  under  the  conditions  employed. 

Action  of  Alkali  on  Ethyl  a-Cyan-ft-pseudoethylthiourea- 
acrylate. — This  ester  is  not  decomposed  by  cold,  dilute  sodium 
hydroxide  solution.  On  the  other  hand,  when  warmed  with 
alkali  it  immediately  dissolved,  giving  the  sodium  salt  of 
2-ethylmercapto-5-cyan-6-oxypyrimidine.  When  the  alkaline 
solution  was  acidified  with  hydrochloric  acid, 

2-Ethylmercapto-^-cyan-  6  -oxy  pyrimidine, 
NH— CO 

I  I 

C2H5SC         CCN,    separated   in   colorless  crystals  melting  at 

II  II 
N CH 

2i8°-2o°  to  an  oil.  It  crystallizes  from  hot  water  in  prisms, 
which  melt  at  222°  to  a  clear  oil  without  effervescence.  The 
pyrimidine  gives  a  strong  test  for  uracil  when  treated  with 
bromine  water  and  barium  hydroxide  solution.2  Nitrogen 
determinations  (Kjeldahl) : 

1  Loc.  cit. 

2  Wheeler  and  Johnson:  J.  Biol.  Chcm.,  3,  183  (1907). 


512  Johnson. 

Calculated  for  Found. 

C7H7ON8S.  I.  II. 

N  23.22  23.0  23.15 

This  pyrimidine  and  2-ethylmercapto-5-carbethoxy-6-amino- 
pyrimidine  are  the  only  products  of  the  reaction  when  pseudo- 
ethylthiourea  is  condensed  with  ethyl  ethoxymethylenecyan- 
acetate  in  alcohol  in  the  presence  of  an  excess  of  alkali. 

Condensation   of   Ethyl   Ethoxymethylenecyanacetate  with   More 
than  One  Molecular  Proportion  of  Pseudoethylikiourea  in 

Alcohol. 

An  alcoholic  solution  of  pseudoethylthiourea  was  prepared 
by  dissolving  20  grams  of  the  hydrobromide  of  pseudoethyl- 
thiourea (1.7  mols.)  in  70  cc.  of  absolute  alcohol  and  then 
adding,  at  o°,  a  solution  of  6.1  grams  of  potassium  hydroxide 
(1.7  mols.)  in  30  cc.  of  95  per  cent,  alcohol.  After  filtering 
from  potassium  bromide,  10.7  grams  of  ethyl  ethoxymethylene- 
cyanacetate  (i  mol.)  were  added  to  the  pseudourea  solution 
at  once  when  there  was  an  immediate  reaction  and  a  thick 
mush  of  crystalline  material  was  obtained.  A  portion  of  this 
material  was  filtered  off  and  washed  with  ether.  It  then 
melted  at  i28°-i3O°.  This  insoluble  substance  was  identified 
as  ethyl  a-cyan-/?-pseudoethylthiourea-acrylate,  which  was  ob- 
tained in  my  previous  condensation  (see  above).  On  evapora- 
ting the  ether  solution  I  obtained  2-ethylmercapto-5-carb- 
ethoxy-6-aminopyrimidine1  which  was  identified  by  its  melt- 
ing point,  IO2°-I03°. 

The  main  portion  of  the  reaction  mixture,  however,  was 
allowed  to  stand,  at  ordinary  temperature,  for  about  2-3 
hours,  when,  to  my  surprise,  practically  all  of  the  acrylic  ester, 
with  the  exception  of  about  1-2  grams,  had  dissolved.  The 
solution  was  then  filtered,  concentrated  on  the  steam  bath,  and 
cooled  whenl  obtained  about  12-13  grams  of  crystalline  material. 
This  was  washed  with  ether  to  remove  any  2-ethylmercapto-5- 
carbethoxy-6-aminopyrimidine,  and  then  triturated  with  cold, 
dilute  sodium  hydroxide  solution.  I  obtained  10.5  grams  of 
a  crystalline  substance  insoluble  in  the  alkaline  solution.  It 

1  Wheeler  and  Johns:  Z,oc.  cit. 


Researches  on  Pyrimidines.  513 

was  soluble  in  hot  water  and  alcohol  and  crystallized  from 
hot  water  in  well-developed  prisms  which  melted  at  164°-  165° 
with  effervescence.  A  nitrogen  determination  agreed  with  the 
calculated  value  for  a-cyan-ft-pseudoethylthiourea-acrylpseudo- 
ethylthiourea,  NH2C(SC2H5)  :NCH  :C(CN)CO.N  :C(SC2H5)NH2. 

Calculated  for 

Found. 


N  24.56  24.43 

When  the  sodium  hydroxide  solution  (above)  was  carefully 
acidified  with  hydrochloric  acid,  2-ethylmercapto-5-cyan-6- 
oxypyrimidine  separated.  It  crystallized  in  prisms  melting 
at  222°  to  an  oil.  Analysis  (Kjeldahl)  : 

Calculated  for 
C7H7ON3S.  Found. 

N  23.22  23.0 

Action   of  Alkali  on  a-Cyan-p-pseudoethylthiourea-acrylpseudo- 
ethylthiourea. 

About  1.5  grams  of  this  compound  were  warmed  with  10 
cc.  of  a  10  per  cent,  aqueous  solution  of  sodium  hydroxide 
for  a  few  minutes.  Ethyl  mercaptan  was  evolved  and  the 
compound  dissolved,  giving  a  clear  solution.  When  this  was 
acidified  with  hydrochloric  acid  2-ethylmercapto-5-cyan-6- 
oxypyrimidine  separated  in  prisms  melting  at  22O°-222°. 
Analysis  (Kjeldahl): 

Calculated  for 
C7H7ON3S.  Found. 

N  23.22  23.16 

Behavior  with  Hydrochloric  Acid.  —  One  gram  of  a-cyan-/?- 
pseudoethylthiourea-acrylpseudoethylthiourea  was  dissolved  in 
about  40-50  cc.  of  concentrated  hydrochloric  acid  and  the 
solution  evaporated  to  dryness.  I  obtained  practically  a 
quantitative  yield  of  5-cyanuracil  (see  below)  which  melted 
without  purification  at  29i°-293°.  After  one  crystallization 
from  water  it  melted  at  293°-295°  and  a  nitrogen  determina- 
tion (Kjeldahl)  gave:  4  * 

Calculated  for 
C5H3O2N3.  Found. 

N  30.6  30.2 


514  Johnson. 

2,6-Dioxy-5-cyanpyrimidine  (5-Cyanuracil) , 
NH— CO 


C.CN.— 


CO      C.CN.  —  A  quantitative  yield  of  this  pyrimidine  was  also 

NH—  CH 

obtained  by  hydrolysis  of  2-ethylmercapto-5-cyan-6-oxypyrimi- 
dine  with  sulphuric  acid  as  follows:  0.7  gram  of  the  mercapto- 
pyrimidine  was  dissolved  in  a  mixture  of  30  cc.  of  alcohol  and 
3  cc.  of  concentrated  sulphuric  acid  and  the  solution  boiled 
until  the  evolution  of  ethyl  mercaptan  ceased.  The  5-cyan- 
pyrimidine  separated  in  hard,  granular  crystals  melting  at 
29i°-292°.  It  is  difficultly  soluble  in  cold  alcohol  and  crystal- 
lizes from  hot  water  in  prisms  which  melt  at  295°  with  de- 
composition. Analysis  (Kjeldahl)  : 

Calculated  for  Found. 

I.  II. 


N  30.6  30.1  30-55 

When  this  pyrimidine  was  digested  with  concentrated 
hydrochloric  acid  for  several  hours  it  was  converted  quan- 
titatively into  uracil.  Analysis  (Kjeldahl)  : 


Calculated  for 
C4H4O2N2.  Found. 


N  25.00  24.6 

NH—  CO 

Uracil-  j-carboxamide,  CO      CCONH2.  —  One  gram  of  2-ethyl- 

I          II 
NH—  CH 

mercapto-5-cyan-6-oxypyrimidine  was  dissolved  in  50  cc.  of 
concentrated  hydrochloric  acid  and  the  solution  evaporated 
to  dryness  on  the  steam  bath.  The  crystalline  material  which 
was  obtained  was  then  dissolved  in  hot  water  and  the  solution 
cooled  slowly,  when  this  pyrimidine  separated  in  small  prisms. 
It  is  difficultly  soluble  in  cold  water  and  does  not  melt  below 
300°.  It  gives  a  strong  test  for  uracil  when  treated  with 
bromine  water  and  barium  hydroxide.  After  heating  for  5 
hours  at  ioo°-iio°  a  nitrogen  determination  (Kjeldahl)  gave: 

Calculated  for 
CsHsOaNa.  Found. 

N  27.00  26.80 


Researches  on  Pyrimidines.  515 

This  amide  was  converted  quantitatively  into  uracil  when 
digested  with  concentrated  hydrochloric  acid. 

The  aqueous  mother  liquor  (above),  after  being  filtered 
from  uracil- 5 -carboxamide,  was  concentrated  to  a  small 
volume  and  cooled,  when  the  characteristic  prisms  of  5-cyan- 
uracil  separated.  After  two  crystallizations  from  hot  water 
it  melted  at  293°-295°.  Analysis  (Kjeldahl) : 

Calculated  for 
CsHaOzNs.  Found. 

N  30.6  30.1 

NEW  HAVEN,  CONN., 
July,  1909. 


[Reprinted  from  The  American  Chemical  Journal, 
Vol.  XI,III.     No.  i.    January,  1910.] 


[Contributions  from  the  Sheffield  Laboratory  of  Yale  University.] 

CLXXVIL— RESEARCHES  ON  PYRIMIDINES: 
THE   THIO    DERIVATIVES    OF   THYMINE   AND   THE 
PREPARATION  OF  THYMINE.1 

[FORTY-NINTH  PAPER.] 

BY  HENRY  L.  WHEELER  AND  DAVID  F.  MCFARLAND. 

In  preparing  uracil  from  ethylpseudothiourea  hydrobromide 
and  the  sodium  salt  of  ethyl  formylacetate,2  for  some  unknown 
reason  it  has  sometimes  happened  that  the  yield  obtained 
was  very  poor.  A  more  satisfactory  result  was  invariably 
obtained  when  sodiumformylacetate  and  thiourea  were  used.3 
The  employment  of  thiourea  instead  of  the  pseudothiourea 
had  the  additional  advantage  of  being  a  more  direct  process. 
It  rendered  unnecessary  the  preparation  of  the  pseudothio- 
urea and  was  therefore  less  expensive,  and,  perhaps  better 
than  all,  the  presence  of  mercaptan  was  avoided. 

These  results  suggested  that  the  preparation  of  thymine 
might  be  improved  in  a  similar  manner.  When  the  sodium 
salt  of  ethyl  formylpropionate  was  condensed  with  thiourea 
in  aqueous  solution  (four  experiments)  we  were  surprised  to 
find  that  the  yield  of  2-thiothymine  (I)  was  invariably  about 
one-half  what  would  be  expected  from  the  pseudothiourea 
condensation  under  similar  conditions.  Obviously  this  was 
no  improvement  over  our  original  method. 

We  have  recently  found,  in  other  cases,  that  certain  /?-ketone 
esters  condense  with  thiourea  in  alcoholic  solution  when  they 

1  Part  of  a  thesis  presented  by  David  F.  McFarland  for  the  degree  of  Ph.D.,  Yale, 
1909. 

2  Wheeler  and  Merriam:  THIS  JOURNAL,  29,  478  (1903). 

3  Wheeler  and  Liddle:  Ibid.,  40,  547  (1908). 


2o  Wheeler  and  McFarland. 

failed  to  do  so  in  water.  The  condensation  of  ethyl  sodium- 
formylpropionate  with  thiourea  was  therefore  carried  out  in 
alcoholic  solution  (eight  experiments).  This  brought  about 
the  desired  improvement.  The  yields  were  over  twice  those 
obtained  in  the  aqueous  condensation. 

For  comparison  with  our  original  method  ethyl  sodium- 
formylpropionate  was  condensed  with  ethylpseudothiourea 
in  aqueous  (four  experiments)  and  alcoholic  (one  experiment) 
solutions.  It  was  then  found  that  the  average  yield  of  2-ethyl- 
mercapto-5-methyl-6-oxypyrimidine,  in  these  experiments, 
when  expressed  in  the  equivalent  weight  of  thymine,  was 
nearly  identical  (20.9  per  cent,  of  the  calculated)  with  that 
calculated  from  the  average  yield  of  2-thiothymine  obtained 
in  the  alcoholic  condensations  (22.6  per  cent,  of  the  calcula- 
ted). 

In  other  words,  almost  the  same  amount  of  thymine  is  ob- 
tained in  these  condensations  whether  we  use  thiourea  in  alco- 
hol or  pseudothiourea  in  water  or  alcohol.  The  use  of  thio- 
urea, however,  gives  a  little  better  yield  and  it  is  also  to  be 
recommended  for  the  reasons  stated  above.  The  condensa- 
tion takes  place  as  follows : 


HNH       C2H5OCO  HN CO  C2H5OH 

I  III 

SC      +  CCH3  =  SC        CCH3  + 

I                      II                  I          II 
HNH          NaOCH          HN CH  NaOH 


It  is  peculiar  that  a  similar  condensation  failed  to  take  place 
in  the  case  of  urea  and  ethyl  sodiumformylpropionate  or 
ethyl  sodiumformylacetate1  in  either  absolute  alcohol  or  aqueous 
solutions. 

2-Thiothymine  (I),  like  2-thiouracil,  is  desulphurized  and 
quantitatively  converted  into  thymine  (V)  by  simply  dis- 
solving in  water  and  evaporating  to  dryness  with  a  slight  ex- 
cess of  chloracetic  acid.  The  thymine  prepared  in  this  manner 

1  Wheeler  and  Liddle:  Loc.  cit. 


Researches  on  Pyrimidines.  21 

melts  higher  and  appears  to  be  more  readily  purified  than 
when  prepared  by  means  of  a  pseudothiourea. 

We  have  prepared  6-thiothymine  (II)  and  2,6-dithiothy- 
mine  (IV)  in  a  manner  similar  to  that  used  in  the  case  of  the 
corresponding  uracil1  and  4-methyluracil  derivatives.2  The 
preparation  of  the  6-thio  derivatives  in  the  thy  mine  series 
is  far  less  satisfactory  than  in  the  case  of  those  previously  de- 
scribed. The  2-ethylmercapto-5-methyl-6-thiopyrimidine 
(III),  on  boiling  with  hydrochloric  acid,  evolves  mercaptan 
less  easily  than  in  the  previous  cases  and  the  sulphur  in  the 
6-position  is  also  more  or  less  removed  at  the  same  time,  so  that 
the  yield  is  poor,  or  nothing  but  thymine  is  obtained.  A 
similar  behavior  was  observed  in  the  preparation  of  6-thiouracil 
but  only  on  long  warming  with  acid.  On  the  other  hand, 
6-thio-4-methyluracil  evolved  mercaptan  smoothly  without 
being  desulphurized  in  the  6-position. 

2, 6-Dithio thymine  (IV)  was  prepared  from  2-ethylmer- 
capto-5-methyl-6-thiopyrimidine  (III)  by  heating  with  dry 
hydrogen  chloride. 

We  have  found  that  the  methylation  of  6-thiothymine  first 
gives  2-oxy-5-methyl-6-methylmercaptopyrimidine  (VI),  as 
would  be  expected,  and  on  further  methylation  this  com- 
pound yields  the  3-methyl  derivative,  2-oxy-3,5-dimethyl-6- 
methylmercaptopyrimidine  (VII).  This  result  is  in  accord- 
ance with  the  general  tendency,  previously  observed  by  us, 
of  a  6-mercapto-2-oxypyrimidine  to  alkylate  in  the  3-posi- 
tion. 

2-Oxy-3,5-dimethyl-6-methylmercaptopyrimidine  (VII),  on 
boiling  with  hydrochloric  acid,  gives  a  quantitative  yield  of 
3-methylthymine  (VIII).  These  compounds  and  their  trans- 
formations may  be  represented  as  follows: 

1  Wheeler  and  Liddle:  Loc.  cit. 

2  Wheeler  and  McFarland:  THIS  JOURNAL,  42,  431  (1909). 


22  Wheeler  and  McFarland. 

HN CS  HN CS  HN CS 

CCH, 


J.JLJ.TI V^WJ  J.JLJ.-*  ^>y-f  JLJL-l.1l 

OC         CCH3  •<—  C2H5SC        CCH3  — •>    SC 


\ 

N=CSCH3  N=CSCH3 

H3  — >•  OC         CCH3 


A  1 -*^*-x' 

OC        CCJ 


HN CH  CH3N CH 

VI.  VII. 


CH3N CH 

VIII. 

EXPERIMENTAL  PART. 

Ethyl  Sodiumformylpropionate,  NaOCH  =  C(CH3)CO2C2H5.— 
This  salt  was  prepared,  as  Wislicenus  directs,1  in  a  manner 
similar  to  that  used  in  the  case  of  ethyl  sodiumformylacetate. 
We  have  obtained  the  best  results  in  the  preparation  of  these 
salts  when  one  atomic  proportion  of  sodium  was  covered  with 
dry  ether  in  a  flask  attached  to  a  return  condenser  and  the 
mixture  of  esters  slowly  added.  An  excess  of  ethyl  formate 
was  employed  and  the  amount  of  ether  was  sufficient  to  pre- 
vent the  mixture  from  becoming  thick.  Three  or  four  times 
the  volume  of  the  mixed  esters  was  usually  sufficient.  If 
evaporation  of  the  ether  took  place,  owing  to  the  esters  being 
added  too  rapidly,  or  if  not  enough  was  present,  the  product 
frequently  was  sticky  and  difficult  or  impossible  to  filter.  It 
therefore  could  not  be  washed  with  ether  and  dried  satisfac- 
torily. When  100  to  150  grams  of  each  ester  were  used  about 
a  day  and  a  half  or  two  days  was  taken  to  add  the  mixture  to 
the  sodium.  The  sodium  disappeared  and  the  reaction  was 
complete  in  about  four  days  altogether. 

In  one  experiment  from  150  grams  of  ethyl  propionate  and 

Ber.  d.  chem.  Ges.,  20,  2934  (1887). 


Researches  on  Pyrimidines.  23 

900  cc.  of  ether  with  one  atomic  proportion  of  sodium  and  1 50 
grams  of  ethyl  formate,  145  grams  of  dry  sodium  salt  were  ob- 
tained. In  the  ether  filtrate  9.6  grams  of  2-thiothymine 
were  found,  or  an  equivalent  of  32 . 3  grams  more  of  sodium 
salt  (see  experiment  XIV  below).  The  total  yield  of  crude 
sodium  salt  was  therefore  177.3  grams  for  150  grams  of  ethyl 
propionate,  or  118.2  grams  for  100  grams  of  ester. 

In  another  experiment  which  was  carried  out  in  the  same 
manner  as  the  above,  50  grams  of  ethyl  propionate  gave  43 . 2 
grams  of  dry  sodium  salt  and  an  amount  of  2-thiothymine 
(4.3  grams)  in  the  ether  filtrate  (experiment  XV)  equivalent 
to  1 6. 8  grams  more  of  salt,  making  a  total  of  60  grams 
or  120  grams  for  100  grams  of  ethyl  propionate.  This 
is  79  per  cent,  of  the  calculated.  (See  also  experiment 
XIII  below.)  In  the  condensations  in  which  we  have  used 
this  crude  salt,  the  yields  of  pyrimidine  derivatives  have  in 
no  case  amounted  to  much  over  30  per  cent,  of  the 
calculated.  The  salt  is  obviously  not  pure,  but  whether  or 
not  this  fact  alone  accounts  for  the  low  yield,  or  whether 
stereochemically  different  salts  exist  here,  one  form  condens- 
ing and  the  other  not,  will  have  to  be  determined  later. 

Preparation  of  2-Ethylmercapto-5-methyl-6-oxy  pyrimidine* 
HN CO 

I  I 

C2H5SC         CCH3. — I.  One  hundred  grams  of  propionic  ester 

II  II 
N CH 

and  80  grams  of  formic  ester  were  added  to  22.5  grams  of 
sodium  covered  with  ether.  The  ethyl  sodiumformylpropion- 
ate  was  not  filtered  off  but  was  condensed  with  100  grams  of 
pseudoethylthiourea  hydrobromide  by  means  of  65  grams  of 
potassium  hydroxide  in  about  750  cc.  of  water.  On  acidify- 
ing with  acetic  acid,  after  warming  the  mixture,  33  grams  of 
2-ethylmercapto-5-methyl-6-oxypyrimidine  melting  at  150° 
were  obtained. 

II.  In  another  experiment  150  grams  of  propionic  ester, 
120  grams  of  formic  ester  and  33.7  grams  of  sodium  were 
used.  The  product  was  mixed  with  a  solution  of  150  grams 
of  ethylpseudothiourea  hydrobromide  and  97  grams  of  potas- 

1  See  Wheeler  and  Johnson:  THIS  JOURNAL,  31,  595  (1904). 


24  Wheeler  and  McFarland. 

suim  hydroxide  in  about  a  liter  of  water.     The  yield  of  mer- 
captopyrimidine  was  57.5  grams. 

III.  This   experiment   was   carried   out   by    Dr.    Victor   C. 
Myers.     One  hundred  and  fifteen  grams  of  propionic  ester, 
TOO  grams  formic  ester  and  26  grams  of  sodium  in  250  cc.  of 
ether  were  taken.     The  sodium  salt  was  not  filtered  off  but 
was  condensed  with  97  grams   of  ethylpseudothiourea  hydro- 
bromide  and   30  grams  of  potassium  hydroxide.     The  solu- 
tion was  allowed  to  stand  for  24  hours  and  then  concentrated 
to  one-half  volume  (300  cc.?)  before  precipitating  with  dilute 
acetic    acid.     The    precipitate    weighed    61.5    grams.     This 
probably  contained  some  potassium  and  sodium  salts  since  on 
recrystallizing  from  water  40  grams  of  material  melting  at 
i58°-i59°  was  obtained. 

IV.  The   above   experiment   was   repeated   with    the   same 
quantities  and  under  the  same  conditions.      The  first  portion 
of  mercapto  compounds  separated  weighed  53 . 3  grams.     When 
recrystallized  from  water  38 . 3  grams  of  pure  material  were  ob- 
tained.    The    mother    liquor    contained    sodium    and    potas- 
sium salts. 

V.  In  this  experiment  the  condensation  was  tried  in  alco- 
hol.    Thirteen  and  a  half  grams  of  dry  ethyl  sodiumformyl- 
propionate  were  mixed  with   16.4  grams  of  ethylpseudothio- 
urea hydrobromide  in  300  cc.  of  absolute  alcohol  in  which  2.0 
grams  of  sodium  had  been  dissolved.     Complete  solution  did 
not  take  place.     The  mixture  was  shaken  and  let  stand  for  20 
hours,   then  warmed  on  the  steam  bath,  evaporated  to  dry- 
ness  and  dissolved  in  60  cc.  of  water  and  precipitated  with 
acetic  acid.     The  precipitate  weighed  3.85  grams. 

The  following  table  gives  a  further  comparison  of  the  above 
results : 


Calculated 

weight  of 

Calculated 

Weight 
of  ethyl 

Weight 
of  ethyl  so- 
diumforrayl- 

Weight  of 
mercapto 
derivative 

mercapto 
derivative 
per  100 

Per  cent, 
yield  of 
mercapto 

weight  of 
thymine 
from  100 

propionate. 

propionate. 

obtained. 

grams  ester. 

derivative. 

grams  ester. 

I      100 

I201 

33-o 

33-o 

19-75 

24.4 

II      I50 

ISO1 

57-5 

38.3 

22.9 

28.4 

HI      II5 

I381 

61.5 

53-3 

31-9 

39-5 

IV    115 

I381 

53-2 

46-3 

27-7 

34-3 

V    ... 

13-5 

3-85 

33-7 

20.2 

24.9 

1  Calculated  from  average  yield  of  salt. 


Researches  on  Pyrimidines.  25 

If  we  exclude  experiments  III  and  IV,  in  which  the  results 
are  a  little  too  high,  as  already  stated,  the  average  yield  of 
thymine  is  25.9  grams  from  100  grams  of  ethyl  propionate 
(or  including  these  results  it  is  30.3  grams).  Twenty-five 
and  nine- tenths  grams  of  thymine  is  20.9  per  cent,  of  the 
theoretical  amount  calculated  directly  from  the  ethyl  pro- 
pionate. 

HN CO 

I  I 

Preparation   of    2-Thiothymine,     SC         CCH3,    in   Alcoholic 

I  II 

HN CH 

Solution. — VI.  Nineteen  grams  of  ethyl  sodiumformylpro- 
pionate,  pressed  on  paper  and  dried  until  all  odor  of  ether  had 
disappeared,  were  added  to  a  solution  of  9.5  grams  (one 
molecule)  of  thiourea  and  2 . 9  grams  of  sodium  in  350  cc.  of 
absolute  alcohol.  The  mixture  was  warmed  for  3  hours, 
evaporated  to  dryness,  dissolved  in  80  cc.  of  water  and  pre- 
cipitated with  dilute  acetic  acid.  The  crystalline  precipitate 
weighed  6 . 8  grams. 

VII.  Twenty-eight  grams  of  the  sodium  salt  were  warmed 
for  five  hours  with  14  grams  (i  molecule)  of  thiourea  in  400 
cc.  of  absolute  alcohol,  then  evaporated  to  dryness,  dissolved 
in  water  and  precipitated  with  acetic  acid.     The  yield  in  this 
case  was  8 .  o  grams. 

VIII.  Fourteen   and   one-tenth   grams   of   the   dry   sodium 
salt  were  treated  with   the  same  relative  proportions  of  the 
thiourea,   sodium  ethylate,   and  alcohol  and  under  the  same 
conditions  as  in  experiment  VI.     The  yield  of  2-thiothymine 
was  3 . 4  grams. 

IX.  Fifteen  grams  of  the  sodium  salt,  4  grams  of  thiourea 
(about  one-half  molecule)  and  2 . 2  grams  of  sodium  dissolved 
in  150  cc.  of  absolute  alcohol  were  mixed  and  heated  for  3 
hours.    Then  25  cc.  of  water  were  added  and  the  whole  evap- 
orated to  dryness.      The  residue   was  taken  up  in  60  cc.   of 
water    and    precipitated    with    acetic    acid.     The    precipitate 
weighed  4 .  o  grams.     On  recrystallizing  from  17.5  cc.  of  alco- 
hol 3 . 4  grams  separated. 


26  Wheeler  and  McFarland. 

X.  Twenty-seven  grams  of  the  sodium  salt  were  warmed 
with  13.5  grams  (one  molecule)  of  thiourea  and  4.3  grams  of 
sodium  in  350  cc.  of  95  per  cent,  alcohol  for  three  and  a  half 
hours.     There    remained    considerable    material    undissolved. 
The  alcohol  was  evaporated  and  the  residue  was  dissolved  in 
140  cc.  of  water.     The  addition  of  acetic  acid  to  this  solution 
gave  8 .  o  grams  of  2-thiothymine. 

XI.  Thirteen  and   two- tenths  grams  of  sodium  salt  were 
warmed  with  3.5   grams  of   thiourea   (a  little   over  one-half 
molecule)  and  2  grams  of  sodium  in  150  cc.  of  95  per  cent, 
alcohol  for  3  hours.     Twenty-five  cc.  of  water  were  added  and 
the  solution  was  warmed  for  a  half  hour,  then  evaporated  to 
dryness.     The  residue  was  taken  up  in  60  cc.  of  water  and 
precipitated,    whereupon    3 . 3    grams   of    2-thiothymine    were 
obtained. 

XII.  Fifteen   grams   of   dry   sodium   salt   were   warmed   3 
hours  with  4  grams  of   thiourea   (one-half  molecule    +    0.5 
gram)  and  2.3  grams  of  sodium  dissolved  in  100  cc.  of  85  per 
cent,  alcohol.     The  sodium  salt  was  first  dissolved  in  15  cc. 
of  water  and  then    the    sodium  ethylate  and  thiourea  were 
added.     Some  solid  separated  after  warming,  10  cc.  more  water 
were  added  and  the  solution  heated  for  a  half  hour  longer. 
On  evaporating  to  dryness,  dissolving  in  60  cc.  of  water  and 
precipitating,    3.8    grams    of    2-thiothymine    were    obtained. 
On  recrystallizing  from  175  cc.  of  water  3.2  grams  separated. 

XIII.  Fifty  grams  of  ethyl  propionate,  43 . 5  grams  of  ethyl 
formate  and  11.3  grams  of  sodium  gave  47 . 5  grams  of  dry 
ethyl  sodiumformylpropionate.     The  ether  filtrate  was  evap- 
orated  to  dryness  and   the   residue  was  combined  with   the 
above.     Calculating  on  the  basis  of  65  grams  of  sodium  salt 
in  the  entire  lot,  twenty  grams  of  thiourea  (over  half  mole- 
cule) in  500  cc.  of  95  per  cent,  alcohol  were  added.     The  mix- 
ture was  heated  three  and  a  half  hours,  the  alcohol  was  then 
evaporated   and   the   residue   dissolved   in    175   cc.   of   water. 
When  precipitated  as  in  the  previous  cases,  15  grams  of  2-thio- 
thymine were  obtained. 

XIV.  The  ether  filtrate  from  a  condensation  in  which  150 
grams  of  ethyl  propionate  were  converted  into  sodium  salt 


Researches  on  Pyrimidines. 


27 


was  evaporated  to  dryness  and  treated  with  4  grams  of  sodium 
in  400  cc.  of  absolute  alcohol  and  20  grams  of  thiourea.  The 
mixture  was  heated  one  hour  on  the  steam  bath  and  then 
evaporated  to  dryness.  Two  hundred  and  fifty  cc.  of  water  were 
added  and  the  solution,  on  precipitating  with  acetic  acid, 
gave  9.6  grams  of  2-thiothymine.  From  the  average  yield 
of  four  condensations  with  the  filtered  salt  it  is  calculated 
that  the  ether  solution  in  this  case  contained  32 . 3  grams  of 
ethyl  sodiumformylpropionate. 

XV.  The  ether  filtrate  from  the  preparation  of  ethyl  so- 
diumformylpropionate in  which  50  grams  of  ethyl  propionate 
were  used  was  treated  as  above  with  3  grams  of  sodium  in 
loo  cc.  of  absolute  alcohol  and  5  grams  of  thiourea.  The  mix- 
ture was  warmed  for  3  hours,  then  35  cc.  of  water  were  added 
and  the  solution  was  warmed  for  a  half  hour  longer.  On 
evaporating  to  dryness,  taking  up  in  50  cc.  of  water,  and  add- 
ing acetic  acid  4.3  grams  of  2-thiothymine  were  obtained. 

The  following  table  gives  the  results  of  the  condensation  of 
ethyl  sodiumformylpropionate  with  thiourea  in  alcoholic  solu- 
tions : 


Calculated 

Number  of 

Weight 

weight 

Calculated 

Weight  of 

cc.  of  alcohol 

of 

of  2-thio- 

Per cent. 

weight  of 

ethyl  so- 
diumformyl- 

for i  gram 
of  sodium 

2-thio- 
thymine 

thymine 
from  100 

yield  of 
2-thio- 

thymine 
from  100 

propionate. 

salt. 

obtained 

grams  ester. 

thymine. 

grams  ester. 

VI 

IQ.O 

18.4 

6.8 

42.3 

30-4 

37-6 

VII 

28.0 

H-3 

8.0 

33-8 

24.2 

30.0 

VIII 

I4.I 

18.4 

3-4 

28.6 

20.5 

25-3 

IX 

15.0 

10.  0 

4.0 

32.0 

23-0 

28.4 

X 

27-0 

13.0 

8.0 

35-o 

25-1 

31.0 

XI 

13.2 

n-3 

3-3 

30.0 

21.6 

26.6 

XII 

15.0 

5-7 

3-8 

30-4 

21.8 

27.0 

XIII 

6O.O? 

8-3 

15-0 

30.0 

20.  1 

24.8 

Experiments  VI,  VII,  VIII  and  IX  were  carried  out  in  ab- 
solute alcohol,  X,  XI  and  XIII  in  95  per  cent,  alcohol,  and 
XII  in  85  per  cent,  alcohol.  Experiment  VIII  is  a  duplicate 
of  VI.  Sodium  ethylate  and  the  calculated  quantity  of  thio- 
urea were  present.  Number  VII  was  similar  except  that  no 
sodium  ethylate  was  used.  In  IX  sodium  ethylate  was  pres- 
ent but  only  one-half  the  calculated  quantity  of  thiourea 


28  Wheeler  and  McFarland. 

was  added.  In  the  remaining  experiments  sodium  ethylate 
and  about  one-half  the  calculated  quantity  of  thiourea  was 
employed,  except  in  X,  where  one  molecular  proportion  of 
thiourea  was  used. 

If  we  exclude  experiment  VI,  which  for  some  unknown  rea- 
son gave  a  much  higher  yield  of  2-thiothymine  than  the  others, 
and  also  experiment  XIII,  in  which  the  amount  of  salt  taken 
was  determined  by  calculation,  we  find  that  the  average  yield 
of  thy  mine  by  this  method  is  28.0  grams  from  100  grams  of 
ethyl  propionate.  This  is  22.6  per  cent,  of  the  calculated. 

Preparation  of  2-Thiothymine  in  Aqueous  Solution. — XVI. 
Seventeen  grams  of  ethyl  sodiumformylpropionate  were  dis- 
solved in  a  solution  of  8.5  grams  (one  molecule)  of  thiourea 
in  65  cc.  of  water.  The  solution  was  allowed  to  stand  for  10 
hours,  then  precipitated  with  acetic  acid.  The  yield  of  2-thio- 
thymine was  2 . 5  grams. 

XVII.  (By  WAITER  F.  STOREY.)     One  hundred  grams  of 
propionic  ester  were  condensed  with  an  excess  of  ethyl  formate 
and  a  little  over  (2  grams)  one  atomic  proportion  of  sodium. 
When  all  the  sodium  had  disappeared  the  calculated  quantity 
(one  molecule)   of  thiourea  was  added  in  ice  water  and  the 
mixture    thoroughly   shaken.     After   standing   overnight    the 
ether  was   removed   and,   after   warming,   concentrating   and 
cooling,  acetic  acid  was  added.     The  yield  was  14.5  grams  of 
the  thiopyrimidine. 

XVIII.  One  hundred  and  fifty  grams  of  ethyl  propionate, 
115  grams  of  ethyl  formate  and  36  grams  instead  of  33.8 
of  sodium  were  used  in  this  experiment.     When  the  sodium 
had  disappeared  a  solution  of  55  grams  of  thiourea  in  400  cc. 
of  water  was  prepared   (38  grams  is  one- half  the  calculated 
amount).     Lumps  of  ice  were  added  to  the  solution  of  the  salt 
and  the  ether  solution.     The  whole  was  shaken  and  allowed  to 
stand   overnight.     The   deep   red   solution   was   concentrated 
on  the  steam  bath  and  finally  cooled  and  acetic  acid  added. 
The  precipitate  weighed   27   grams,   and  from   the  filtrate  3 
grams  more  were  obtained  on  standing. 

XIX.  One   hundred   grams   of   each   ester   were   condensed 
with  2  grams  more  than  the  calculated  amount  of  sodium. 


Researches  on  Pyrimidines.  29 

The  whole  was  mixed  with  a  saturated  solution  of  70  grams 
of  thiourea  in  ice  water.  After  standing  a  few  minutes  it 
was  warmed  and  acetic  acid  added.  Fifteen  grams  of  2-thio- 
thymine  were  obtained. 

The  following  table  gives  the  results  of  the  condensation  of 
ethyl  sodiumformylpropionate  with  thiourea  in  aqueous  solu- 
tion. 


Calculated 

weight  of 

Calculated 

Weight  of 

Weight    2-thio- 

weight  of 

ethyl 

of        thymine 

Per  cent. 

thymine 

Weight  of 

sodium- 

2-thio-   from  100 

yield  of 

from 

propionic 
ester. 

formyl- 
propionate. 

thymine    grams 
obtained,    ester. 

a-thio- 
thymine 

100  grams 
ester. 

i?1 

2-5          17-4 

12.5 

15-4 

100 

I201 

14-5          H-5 

10-4 

12.8 

150 

iSo1 

30.0       20.  o 

14.4 

17.7 

IOO 

I201 

15.0          15.0 

10.7 

13-3 

XVI 

XVII 

XVIII 

XIX 

The  average  yield  of  thymine  by  this  method  is  14.8 
grams  from  100  grams  of  ethyl  propionate.  This  is  only  11.9 
per  cent,  of  the  calculated. 

HN CO 

I  I 

The  Preparation  of  Thymine,  OC         CCH3. — It  was  shown  by 

I  II 

HN CH 

Wheeler  and  Merriam  that  2-methylmercapto-5-methyl-6- 
oxypyrimidine2  gave  99  per  cent,  of  the  calculated  amount  of 
thymine  when  boiled  with  hydrochloric  acid.  The  ethyl- 
mercapto  derivative  gives  a  similar  result. 

2-Thiothymine,  like  2-thiouracil,  is  easily  desulphurized  by 
simply  evaporating  its  aqueous  solution  with  chloracetic 
acid.3  For  example,  3  grams  of  2-thiothymine  were  dissolved 
in  250  cc.  of  boiling  water  and  3  grams  of  chloracetic  acid 
were  added.  The  solution  was  then  evaporated  to  dry  ness 
on  the  steam  bath  and  the  residue  was  washed  with  15-20  cc. 
of  alcohol.  It  was  free  from  sulphur  and  weighed  2.55 
grams  or  95 . 8  per  cent,  of  the  calculated.  On  evaporating 
the  alcoholic  washings  more  was  obtained.  The  washed  ma- 

1  Calculated  from  average  yield  of  salt. 

2  THIS  JOURNAL,  29,  487  (1903). 

3  Ibid.,  40,  552  (1908). 


30  Wheeler  and  McFarland. 

terial  consisted  of  snow-white  crystals  or  scales  and  it  melted 
at  340°.  This  is  a  higher  melting  point  than  that  observed 
for  thymine  from  other  sources.  Fischer  and  Roeder1  give 
321°,  Wheeler  and  Merriam2  326°.  A  nitrogen  determina- 
tion by  W.  F.  Storey  gave: 

Calculated  for 
C6H6O2N2.  Found. 

N  22.22  22.21 

In  desulphurizing  larger  quantities  it  is  unnecessary  to  dis- 
solve all  the  material  at  first  and  relatively  less  chloracetic 
acid  may  be  used. 

Properties  of  2-Thiothymine. — The  properties  of  2-thio- 
thymine  and  its  salts  have  been  investigated  by  W.  F.  Storey. 
When  the  substance  is  first  obtained  by  acidifying  the  alka- 
line solutions  with  acetic  acid  it  separates  slowly,  usually  not 
all  at  once,  as  a  crystalline  brownish- white  precipitate.  It 
has  about  the  same  solubility  in  water  as  in  alcohol  and  it 
crystallizes  from  these  solvents  in  fairly  stout  prisms,  which 
have  a  tendency  to  retain  the  color  of  the  solutions.  One  hun- 
dred parts  of  water  at  20°  dissolved  0.133  part  of  2-thio- 
thymine.  This  is  the  average  of  two  closely  agreeing  deter- 
minations. Thymine  is  more  than  twice  as  soluble  in  water. 
Mr.  Storey  found  that  100  parts  of  water  at  23°  dissolved 
0.303  part  thymine. 

Calculated  for 

C6H6ON2S.  Found. 

N  19-71  19-67 

2-Thiothymine  has  more  pronounced  acid  properties  than 
thymine.  When  crystallized  from  aqueous  ammonia  it  re- 
tains ammonia.  On  drying,  the  amount  of  ammonia  re- 
tained (21.86  per  cent,  nitrogen)  was  less  than  that  calcula- 
ted for  a  i  :  i  salt  (26.41  per  cent,  nitrogen).  The  salts  of 
the  alkali  metals  are  very  soluble  in  water.  A  solution  of 
the  sodium  salt  gave  with  silver  nitrate  an  amorphous  white 
precipitate,  which  did  not  blacken  on  boiling.  The  boiling 

1  Ber.  d.  chem.  Ges.,  34,  3751  (1901). 

2  Loc.  cit. 


Researches  on  Pyrimidines.  31 

aqueous  solution  gives  a  white  precipitate  with  mercuric 
chloride.  It  did  not  blacken  on  boiling  alone  or  in  the  pres- 
ence of  alkali. 

The  sodium  salt  of  2-thiothymine,  C5H5ON2SNa.i.5H2O,  ap- 
pears to  be  less  soluble  than  the  potassium  salt.  It  was  formed 
by  dissolving  the  pyrimidine  in  water  containing  the  calcula- 
ted quantity  of  sodium  hydroxide,  concentrating  and  then 
crystallizing  from  aqueous  alcohol.  It  formed  radiating 
prisms  which  did  not  melt  at  300°. 

Calculated  for  Found. 

C5HBON2SNa.i.5H20. 


N  14.73  14.73  14.58 

H2O  14.21  14.65 

The  potassium  salt,  C5H5ON2SK.H2O,  is  soluble  in  less  than 
three  parts  of  water.  From  dilute  alcohol  it  forms  radiating, 
colorless  prisms,  similar  to  the  sodium  salt. 

Calculated  for 
C6H6ON2SK.H2O.  Found. 

N  14.14  '13-83 

The  Copper  Salt,  C5H4ON2SCu.H2O.—  This  salt  was  prepared 
by  adding  copper  sulphate  in  aqueous  solution  to  a  hot  satura- 
ted aqueous  solution  of  2-thiothymine.  It  formed  a  green, 
amorphous  precipitate,  which  was  washed  with  water  and 
dried  over  sulphuric  acid. 

Calculated  for 

oO.  Found. 


N  12.58  12.52 

H2O  8.08  7.79 

It  may  be  mentioned  that  the  corresponding  copper  salt 
of  2-thiouracil,  which  also  contains  one  molecule  of  water,1 
has  a  mustard-yellow  color.  These  salts  do  not  blacken  on 
boiling.  List2  found  that  2-thio-4-methyluracil  in  hot,  satura- 
ted, aqueous  solution  gave  a  yellow  precipitate  with  copper 
sulphate  (this  salt  was  anhydrous),  while  if  the  potassium 
salt  was  used  a  green  copper  salt  was  obtained. 

1  Wheeler  and  Liddle:  Loc.  cit. 

2  Ann.  Chem.  (Liebig),  236,  9.  11  (1886). 


32  Wheeler  and  McFarland. 

2-Benzylmercapto-5-methyl-6-oxypyrimidine, 
HN CO 

I  I 

C6H5CH2SC        CCH3  (By  W.  F.  STOREY)  .—This  was  prepared 

II  II 
N CH 

from  the  above  potassium  salt  by  warming  in  alcoholic  solu- 
tion with  benzyl  chloride.  From  dilute  alcohol  it  formed 
colorless  needles,  which  melted  to  a  clear  oil  at  2O4°-2O5°. 

Calculated  for 
Ci,HltON2S.  Found. 

N  12.07  12.25 

2-  Ethylmer  capto-j-  methyl-  6  -  thiopyrimidine , 
HN CS 

I  I 

C2H5SC         CCH3. — An  alcoholic  solution  of  potassium  hydro- 

II  II 
N CH 

sulphide  was  prepared  by  saturating  a  solution  of  57  grams 
of  potassium  hydroxide  in  250  cc.  of  alcohol  with  hydrogen 
sulphide.  To  this  solution  24  grams  of  2-ethylmercapto-5- 
methyl-6-chlorpyrimidine1  were  added.  The  reaction  began 
immediately  and  after  warming  on  the  steam  bath  for  nearly 
an  hour  the  solution  was  evaporated  to  dryness.  The  resi- 
due dissolved  completely  in  water  and  on  acidifying  with 
acetic  acid  a  bulky  precipitate  separated.  After  washing  with 
water  and  drying  it  was  found  that  the  yield  was  practically 
quantitative.  The  crude  material  melted  at  about  175°  to  a 
clear  oil  and  on  further  heating  it  solidified  at  i8o°-i9O°  and 
remained  solid  until  280°  was  reached,  when  it  melted  with 
some  effervescence.  The  substance  dissolved  easily  in  boiling 
alcohol.  When  the  solution  was  quickly  cooled  the  material 
crystallized  in  plates,  but  when  allowed  to  cool  slowly,  pris- 
matic needles  separated.  It  then  melted  at  181°  to  a  clear 
oil ;  the  pure  material,  on  further  heating,  did  not  solidify. 

Calculated  for 
C7Hi0NsSa.  Found. 

N  I5-°5  I4-9I 

1  Wheeler  and  Johnson:  THIS  JOURNAL,  81,  595   (1904). 


Researches  on  Pyrimidines.  33 

HN CS 

I  I 

2,6-Dithiothymine,    SC         CCH3.— Two    grams    of    2-ethyl- 

I  II 

HN CH 

mercapto-5-methyl-6-thiopyrimidine  were  heated  in  an  oil 
bath  at  215°.  The  substance  melted  and  a  small  portion 
sublimed.  On  passing  perfectly  dry  hydrogen  chloride  into 
the  molten  mass  the  material  almost  immediately  solidified. 
The  passage  of  the  gas  was  continued  for  about  five  minutes. 
After  cooling,  the  solid  was  treated  with  ammonium  hydrox- 
ide, which  dissolved  the  greater  part,  leaving  a  small  amount 
of  a  pungent  smelling  oil.  This  was  separated  from  the  am- 
monia solution  and  the  latter  was  acidified  with  acetic  acid. 
A  bulky  yellow  precipitate  resulted,  which  was  only  slightly 
soluble  in  water  but  dissolved  fairly  easily  in  alcohol,  and  then, 
on  cooling,  gave  bunches  of  small,  bright  yellow  needles.  They 
melted  at  281°  with  decomposition  and  effervescence. 

Calculated  for 
C6H6N2S2.  Found. 

N  17.94  18.14 

HN CS 

I  I 

6-Thiothymine,      OC         CCH3.— When     2-ethylmercapto-5- 


HN- 


CH 

methyl-6-thiopyrimidine  is  heated  with  strong  hydrochloric 
acid  it  does  not  smoothly  go  into  6-thiothymine  as  might  be 
expected  from  analogy  with  the  corresponding  4-methyl 
compound,  but  instead  it  shows  a  strong  tendency  to  lose 
sulphur  from  the  6-position  and  pass  directly  into  thymine. 
In  fact,  by  boiling  ten  grams  of  the  2-ethylmercapto-6-thio- 
pyrimidine  for  one  and  a  half  hours  with  strong  hydrochloric 
acid  and  then  twice  evaporating  to  dryness  with  additional 
acid,  very  pure  thymine  was  obtained  which,  after  one  recrys- 
tallization,  gave  no  test  for  sulphur  and  melted  at  340°.  A 
nitrogen  determination  gave  22.22  per  cent,  nitrogen.  This 
is  the  calculated  value  for  thymine. 

By  a  less  vigorous  treatment  with  acid,  the  decomposition 


34  Wheeler  and  McFarland. 

was  not  carried  so  far  and  a  small  yield  of  6-thiothymine  was 
obtained.  Several  experiments  were  required  to  show  the  con- 
ditions best  adapted  to  obtaining  this  result.  It  was  found 
advisable  to  stop  the  hydrolysis  while  there  still  remained 
some  unchanged  mercapto  derivative.  This  was  then  ex- 
tracted by  means  of  alcohol,  leaving  a  mixture  of  6-thiothy- 
mine with  a  small  amount  of  thymine.  These  were  separa- 
ted by  crystallizing  from  water. 

Nine  grams  of  2-ethylmercapto-5-methyl-6-thiopyrimidine 
were  twice  evaporated  to  dryness  on  the  steam  bath  with  45 
cc.  of  concentrated  hydrochloric  acid  and  an  equal  quantity 
of  water.  The  dry  residue  was  boiled  for  a  few  minutes  with 
loo  cc.  of  alcohol  and  the  portion  which  remained  undissolved 
was  filtered  off.  This  weighed  4.2  grams.  It  was  dissolved 
in  boiling  water  and  on  cooling  gave  bright  yellow,  matted, 
silky  needles,  which  melted  with  some  effervescence  at  330°. 

Calculated  for 
C5H6ON,S.  Found. 

N  19-72  J9-98 

2-Oxy-5-methyl-6-methylmercaptopyrimidine, 
N=CSCH3 

I  I 

OC        CCH3. — Four  grams  of  6-thiothymine  were  dissolved 


HN- 


CH 

with  1.58  grams  of  potassium  hydroxide  in  125  cc.  of  alcohol 
and  20  cc.  of  water.  The  change  from  the  yellow  pyrimidine 
to  the  potassium  salt  was  marked  by  an  immediate  change  to 
a  white  color.  Four  grams  of  methyl  iodide  were  added  to 
the  solution  and  the  mixture  was  warmed  for  15  minutes  on 
the  water  bath  and  then  allowed  to  stand  overnight.  The  re- 
action was  complete  at  the  end  of  this  time  and  the  solution 
became  neutral.  The  alcohol  was  evaporated  and  the  resi- 
due was  found  to  be  easily  soluble  in  hot  water.  On  crystal- 
lizing from  this  solvent  bunches  of  light  yellow,  prismatic  needles 
were  obtained  which,  after  two  recrystallizations  from  alco- 
hol, melted  at  205  °-2 1 1  °. 

Calculated  for  Found. 

C6H8ONSS.  I.  ^  II. 

N  17.94  18.08  18.14 


Researches  on  Pyrimidines.  35 

2-Oxy-3,5-dimethyl-6-methylmercaptopyrimidine, 
N=CSCH3 

I  I 

OC        CCH3. — Four    and     seven- tenths   grams   of   potas- 

I          II 
CH3N CH 

slum  hydroxide  and  4.4  grams  of  2-oxy-5-methyl-6-methyl- 
mercaptopyrimidine  were  dissolved  in  150  cc.  of  95  per  cent, 
alcohol.  Twelve  grams  of  methyl  iodide,  or  three  molecular 
quantities,  were  added  and  the  mixture  was  warmed  for  an 
hour  on  the  steam  bath  under  a  return  condenser.  The  solu- 
tion then  became  neutral.  After  evaporating  off  the  alcohol, 
the  solid  residue  was  extracted  three  times  with  boiling  chloro- 
form. An  oily  residue  separated  from  the  chloroform  solu- 
tion which  solidified  to  a  white  solid  on  being  stirred.  It 
weighed  4.5  grams,  or  94  per  cent,  of  the  theoretical  amount 
of  dime  thylme  thy  Imercaptopyrimidine.  This  material  was 
extremely  soluble  in  alcohol.  It  also  dissolved  easily  in  boil- 
ing water  and  benzene.  From  benzene  solutions  it  crystaj- 
lized  in  clusters  of  crystals  resembling  grains  of  wheat.  From 
the  water  solutions,  which  had  a  marked  tendency  to  remain 
supersaturated  even  after  standing  several  hours,  the  sub- 
stance crystallized  in  white,  prismatic  needles,  which  melted 
to  a  colorless  oil  at  83  °. 

Calculated  for 
C7Hi0ON2S.  Found. 

N  16.4  16.6 

Treatment  with  Hydrochloric  Acid:  j-Methylthymine. — In 
order  to  determine  the  structure  of  the  above  compoud  two 
grams  of  it  were  boiled  for  3  hours  with  25  cc.  of  concentrated 
hydrochloric  acid  and  an  equal  quantity  of  water,  under  a 
return  condenser.  On  evaporating  off  the  acid  i .  4  grams  of  a 
white  solid  was  left  behind,  which  melted  at  28i°-283°.  One 
crystallization  of  this  from  water  gave  one  gram  of  material 
melting  at  284°  and  exhibiting  all  the  properties  of  3-methyl- 
thymine,  as  described  by  Johnson  and  Clapp.1  Especially 
noticeable  were  the  two  forms  of  crystals  (needles  and  prisms) 

1  J.  Biol.  Chem.,  d(^49  (1908). 


36  Wheeler  and  McFarland. 

described.     When  this  sample  was  mixed  with  a  sample  of 
their  material  the  melting  point  was  unchanged. 


Calculated  for 

Found. 


N  2O.  O  20.1 

The  mother  liquor  from  this  compound  was  carefully  ex- 
amined for  the  isomeric  i-methylthymine,  but  this  substance 
was  not  found. 

In  order  to  determine  whether  or  not  any  of  the  isomeric 
2-oxy-i,5-dimethyl-6-methylmercaptopyrimidine  had  been 
formed  with  the  3,5-dimethyl  derivative,  the  mother  liquors 
from  the  crystallization  of  2-oxy-3,5-dimethyl-6-methyl- 
mercaptopyrimidine  were  boiled  for  3  hours  with  hydrochloric 
acid,  under  a  return  condenser.  After  evaporating  the  acid 
the  solid  residue  weighed  i  .  i  grams.  From  this,  by  crystal- 
lizing from  water,  were  recovered  0.8  gram  of  nearly  pure 
3-methylthymine,  melting  at  275°-28i°  and  showing  the 
characteristic  properties.  There  was  also  obtained  a  very 
small  quantity  (0.15  gram)  of  another  substance  which  sub- 
limed in  white  needles.  This  substance  melted  at  153°-  155° 
and  was  extremely  soluble  in  water  and  alcohol.  Not  enough 
was  obtained  for  analysis,  but  it  is  probable  that  it  was  1,3- 
dimethylthymine,  described  by  Johnson  and  Clapp.  They 
give  the  melting  point  as  153°.  When  our  material  was 
mixed  with  theirs  the  melting  point  was  not  lowered.  The 
formation  of  i,3-dimethylthymine  may  be  explained  by  sup- 
posing a  small  amount  of  thymine  to  have  been  left  in  the 
6-thiothymine.  The  difficulty  of  obtaining  6-thiothymine 
free  from  thymine  has  been  noted  above.  Thymine,  on  methyl- 
ation,  would  give  i,3-dimethylthymine. 

No  evidence  could  be  found  here  of  the  presence  of  i-methyl- 
thymine.  It  seems  fair  to  conclude,  therefore,  that  under 
the  conditions  employed  in  the  methylation  of  this  6-methyl- 
mercaptopyrimidine  only  a  3-derivative  was  formed. 

NEW  HAVKN,  CONN.; 
September,  1909. 


VII.     ON  SOME  PICROLONATES:     GUANIDINS. 

BY  HENRY  L.  WHEELER  AND  GEORGE  S.  JAMIESON. 

(From  the  Sheffield  Laboratory  of  Yale  University,) 

(Received  for  publication,  December  13,  1907.) 

In  a  paper  recently  published  by  one  of  us1  on  some  salts  of 
cytosin,  isocytosin,  6-aminopyrimidin  and  6-oxypyrimidin  the 
melting  or  effervescing  points  of  the  picrolonates  were  given. 
When  the  these  salts  were  first  prepared  it  was  found  that  Kjel- 
dahl's  method  of  analysis  gave  low  results.  The  method  was  as 
follows:  About  0.11—0.12  gram  of  substance  was  added  to  20  cc. 
of  sulphuric  acid,  then  2  or  more  grams  of  zinc  dust  and  finally  15 
grams  of  potassium  sulphate ;  the  digestion  then  being  carried  on 
as  usual.  On  the  other  hand  this  method  proved  successful  in 
the  case  of  the  corresponding  picrates. 

The  picrolonic  acid  which  we  used  was  obtained  from  Kahl- 
baum.  It  was  shown  to  be  a  pure  sample  by  an  absolute  nitro- 
gen determination  and  by  a  carbon  and  hydrogen  determina- 
tion, but  the  analysis  of  this  material  by  Kjeldahl's  method 
also  gave  results  that  were  several  per  cent  less  than  the  calcu- 
lated. 

The  difficulty  was  finally  found  to  be  due  to  the  insolubility  of 
picrolonic  acid  in  concentrated  sulphuric  acid  since  Kjeldahl's 
procedure  gave  results  agreeing  with  the  calculated  when  the 
reduction  was  carried  out  in  dilute  sulphuric  acid  with  the  addi- 
tion of  some  alcohol.  Although  numerous  picrolonates  have 
recently  been  described  it  appears  that  nitrogen  in  these  salts 
has  invariably  been  determined  by  the  absolute  method.2 

Before  correct  results  had  been  obtained  in  the  analysis  of  our 
sample  of  picrolonic  acid  and  in  order  to  identify  the  material 

1  This  Journal,  iii,  p.  285,  1907. 

2  For  a  list  of  papers  on  picrolonates  up  to  the  year  1907,  see  Matthes 
and  Rammstedt:  Archiv  d.  Pharmazie,  ccxlv,  p.  112,  1907.       Since    then, 
Levene:  Biochem.  Zeitschr.,  iv,  p.  320,  1907,  and  Warren  and  Weiss:  This 
Journal,  iii,  p.  327,  1907. 


ii2  On  Some  Picrolonates  :     Guanidins 

the  guanidin  salt  was  prepared.  This  salt  agreed  in  properties 
with  the  description  of  guanidin  picrolonate  given  by  Schenck.1 

The  action  of  aqueous  solutions  of  amines,  primary  or  second- 
ary, or  ammonia  on  the  alkylhalide  addition  products  of  thio- 
ureas  affords  a  very  convenient  method  for  the  preparation  of 
certain  substituted  guanidins,  especially  those  that  have  been 
found  in  meat  extract2  and  urine.3 

The  action  takes  place  at  ordinary  temperature,  mercaptan  is 
liberated,  and  on  evaporating,  a  guanidin  salt  is  obtained.  For 
example,  when  the  methyl  iodide  addition  product  of  thiourea,  I 
(2-methylpseudothioureahydriodide),  was  dissolved  in  an  excess 
of  a  33  per  cent  solution  of  dimethylamine  bubbles  of  methyl  - 
mercaptan  escaped.  After  evaporating  off  the  excess  of  amine 
by  warming,  then  adding  a  hot  aqueous  solution  of  picrolonic 
acid,  unsymmetrical  dimethyl  guanidin  (2,  2 -dimethyl  guanidin) 
picrolonate  separated.  This  salt  agreed  with  the  description  of 
dimethyl  guanidin  picrolonate  given  by  Kutscher.4 

NH2  NH2  NHCH3  NHCH3 

II  II 

CH3SCI  -»  (CH3)2NCI  C2H5SCBr  ->  CH3NHCBr 

II  II 

NH2  NH2  NH2  NH2 

I  II  III  IV 

The  hydrobromide  of  the  isomeric  symmetrical  dimethyl 
guanidin,  IV.; (i,  2-dimethyl  guanidin),  was  obtained  by  treat- 
ing the  ethylbromide  addition  product  of  methyl  thiourea,  III, 
( i -methyl- 2-ethylpseudothiourea)  with  methylamine. 

The  melting  point  of  the  picrolonate  prepared  from  this 
substance  was  identical  with  that  assigned  to  symmetrical  di- 
methyl guanidin  picrolonate  by  Schenck.5 

Monomethyl  guanidin  hydrobromide  was  prepared  in  two  ways, 
by  dissolving  the  ethylbromide  addition  product  of  thiourea  in 
an  aqueous  solution  of  methylamine  and  by  dissolving  the  corre- 
sponding addition  product  of  methylthiourea  in  concentrated 

1  Zeitschr.  f.  physiol.  Chem.,  xliv,  p.  427,  1905. 

2  Kutscher  and  Lohmann:  Zeitschr.  f.  physiol  Chem.,  xlviii,  p.  i,  1906. 

3  Achelis:  Ibid.,  1,  p.  10,  1906;  Kutscher:  Ibid,  li,  p.  457,  1907. 

4  Loc.  cit. 

5  Zeitschr.  f.  physiol.  Chem.,  xlviii,  p.  423,  1906. 


Henry  L.  Wheeler  and  George  S.  Jamieson    113 

ammonia.  As  would  be  expected  from  the  non-existence  of 
tautomeric  forms  in  the  case  of  the  amidines1  the  picrolonates 
of  the  material  prepared  by  these  two  methods  were  identical. 
The  reactions  and  the  substances  may  be  represented  as  follows : 

(i)NH2  (i)NH2 

I  I 

CH3NH2  +  (2)  C2H5S  -  C  -  Br  =  (2)  CH3NH  -  C  -  Br   +  C2H5SH. 

I  I 

(3)NH2  (3)NH2 

CH3NH  CH3NH 

I  I 

NH3  +  C2H5S  -  C  -  Br         =         H2N  -  C  -  Br  +  C2H5SH. 

I  I 

NH2  NH2 

The  nomenclature  hitherto  employed  for  pseudothioureas  and 
guanidins  (symmetrical  and  unsymmetrical)  is  not  sufficient  to 
define  substituted  derivatives  in  general.  The  writer  therefore 
proposes  to  use  that  system  which  has  been  found  so  convenient 
in  the  purin2  and  pyrimidin  series,  namely,  of  assigning  numbers 
(as  shown  above)  to  indicate  the  position  of  substituents  in  the 
case  of  the  pseudourea,  pseudothiourea  and  guanidin  derivatives. 
Dieckmann3  has  used  this  system  for  parabanic  acid  compounds. 

This  then  brings  about  a  systematic  nomenclature  for  all  these 
related  substances. 

EXPERIMENTAL    PART. 

Cytosin  Picrolonate,  C4H5ON3.C10H8O5N4. — A  half  a  gram  of 
cytosin  in  a  100  cc.  of  water  was  added  to  one  gram  of  picrolonic 
acid  in  about  350  cc.  of  hot  water.  On  rapidly  cooling  the  solu- 
tion an  amorphous,  gelatinous  precipitate  separated.  On  slowly 
cooling  or  on  crystallizing  from  water  little  balls  of  fine  bright 
yellow  needles  or  slender  prisms  separated.  This  salt  is  very 
difficultly  soluble  in  alcohol  from  which  it  is  obtained  in  flat 
prisms  or  plates.  It  melts  with  effervescence  about  27o°-273°. 

The  nitrogen  determinations  in  the  case  of  this  and  the  other 
picrolonates  were  determined  by  Kjeldahl's  method  as  follows: 

1  Wheeler  and  Johnson:  Amer.  Chem.  Journ.,  xxxi,  p.  577,  1904. 

2  Ber.  d.  deutsch.  chem.  Gesellsch.,  xxx,  p.  549,  1897. 

3  Ibid.,  xl,  p.  3737,  1907. 


H4  On  Some  Picrolonates  :    Guanidins 

About  o.i  gram  of  substance  was  dissolved  in  a  mixture  of  35  cc. 
of  alcohol  and  20  cc.  of  dilute  sulphuric  acid.  Two  grams  of 
zinc  dust  were  used  for  the  reduction  and  the  solution  was 
warmed  until  colorless.  Then  10  cc.  of  concentrated  sulphuric 
acid  and  12  grams  of  potassium  sulphate  were  added,  the  water 
and  alcohol  was  evaporated  and  the  residue  was  digested  for  two 
or  three  hours.  The  analysis  was  then  finished  in  the  usual 
manner. 

Calculated  for 
Ci4H13O6N7:  Found: 

N  ........................          26.13  26.15 

Since  this  salt  was  prepared  by  us  it  has  been  obtained  by 
Levene.1  He  gives  the  formula  C4H6N3.C10H8N4O5,  which  is 
evidently  a  typographical  error. 

2-Amino-6-oxypyrimidin  (Isocytosin)  Picrolonate  ,  C4H5ON3, 
C10H8O5N4.  —  A  half  a  gram  of  isocytosin  and  1.2  gram  of  picro- 
lonic  acid,  on  mixing  the  hot  aqueous  solutions  (about  400  cc.), 
gave  an  immediate,  bulky  precipitate  consisting  of  very  fine, 
yellow  hair-like  needles.  This  salt  is  practically  insoluble  in 
alcohol  and  its  melting  or  effervescing  point  varies  with  the  rate 
of  heating.  It  usuallv  decomposes  about  273°-  275°. 

Calculated  for 

Found: 


N  ......  .  .................         26.13  26.05    ' 

6-Aminopyrimidin  Picrolonate,  C4H5N3.C10H8O5N4.  —  A  solution 
of  o.i  gram  of  6-aminopyrimidin  in  4  cc.  of  water  was  added  to 
0.3  gram  picrolonic  acid  in  100  cc.  of  hot  water.  This  gave  an 
immediate  precipitate  and  on  cooling,  the  salt  separated  in  the 
form  of  interlaced,  yellow,  hairlike  needles.  The  yield  was  0.35 
gram,  calculated,  0.4  gram.  It  melted  with  effervescence  at  261°  ; 
on  rapidly  heating  it  melted  a  few  degrees  higher. 

Calculated  for 
Ci4H,305N7:  Found: 

N  .....  ...................         27.29  27.10 

6-Oxypyrimidin  Picrolonate,  C4H4ON2.C10H8O5N4.  —  A  solution 
of  0.2  gram  of  6-oxypyrimidin  in  6  cc.  of  water  was  added  to 
a  hot  solution  of  0.55  gram  picrolonic  acid  in  125  cc.  of  water. 

1  Biochem.  Zeitschr.,  iv,  p.  320,   1907. 


Henry  L.  Wheeler  and  George  S.  Jamieson     115 

This  gave  an  immediate  precipitate  and  on  cooling,  a  bulky  mass 
of  slender,  yellow  needles  separated.  The  yield  was  0.55  gram. 
When  this  was  heated  it  showed  signs  of  change  at  1  80°  and  then 
melted  with  vigorous  effervescence  at  222°.  The  salt  wasrecrys- 
tallized  from  water  and  from  alcohol.  It  then  melted  suddenly, 
in  both  cases,  at  i9i°-i93°  It  is  difficultly  soluble  in  alcohol 
and  it  separates  from  this  solvent  in  thin  scales  or  plates. 

Calculated  for 

Found: 


N  .........  ...............          23.33  23.33 

MethylguanidinPicrolonate,  C2H7N3.C10H8O5N4.  —  2-Ethyl-pseu- 
dothiourea  hydrobromide  was  dissolved  in  an  excess  of  a  33  per 
cent  solution  of  methylamine  and  allowed  to  stand  over  night. 
The  excess  of  amine  and  mercaptan  was  then  evaporated  and  the 
solution,  after  filtering  from  a  slight  turbidity,  was  divided  into 
two  parts.  One  part  was  precipitated  with  picric  acid;  the 
picrate  formed  needles  which  melted  sharply  at  200°.  Fischer1 
gives  the  melting  point  of  methyl  guanidin  picrate  at  200°. 

The  remaining  solution  was  precipitated  with  an  aqueous  solu- 
tion of  picrolonic  acid.  The  salt  formed  a  compact,  not  bulky, 
yellow  precipitate  which  when  recrystallized  from  water  formed 
minute,  diamond  shaped  tables  or  blocks.  It  decomposed  with 
effervescence  at  291°. 

Calculated  for 
Ci2Hi5O5N7:  Found: 

N  ........................          28.24  28.23 

i-Methylguanidin  was  also  prepared  by  dissolving  1.5  gram  of 
i-methyl-2-ethylpseudothiourea  hydrobromide  in  concentrated 
ammonia.  On  evaporating  the  solution  and  adding  an  aque- 
ous solution  of  picrolonic  acid  the  precipitate  obtained  was  iden- 
tical with  the  above. 

2  ,2-Dimethylguanidin  Picrate,  C3H9N3.C6H3O7N3.  —  The  guani- 
din was  prepared  by  dissolving  2-ethylpseudothiourea  hydro- 
bromide  in  a  strong,  aqueous  solution  of  dimethylamine.  The 
precipitate  produced  by  adding  an  aqueous  solution  of  picric 
acid  was  crystallized  from  water.  It  formed  small,  pointed, 

1  Ber.  d.  deutsch.  chem.  Gesellsch.  xxx,  p.  2414,  1897. 


n6  On  Some  Picrolonates  :     Guanidins 

yellow  prisms  or  branch-like  growths.     It  melted  to  an  oil  with- 
out effervescence  at  224°. 

Calculated  for 
C9H1207N6:  Found: 

N 26.58  26.53 

2,2-Dimethylguanidin  Picrolonate ,  C3H9N3.C10H8O5N4. — The 
guanidin  was  prepared  as  above  and  also  by  the  action  of  dimethyl  - 
amine  on  2-methylpseudothiourea  hydriodide.  The  solutions- 
gave  an  immediate  precipitate  with  aqueous  picrolonic  acid. 
The  salt  was  crystallized  from  water,  it  then  formed  small,  flat, 
four-sided,  yellow  prisms  which  decomposed  with  effervescence 
quite  sharply  at  278°.  Kutscher  and  Lohmann  give  the  melting 
point  of  their  dimethylguanidin  picrolonate  obtained  from 
urine  at  275°-278°.1 

This  salt  is  very  difficultly  soluble  in  alcohol  from  which  it 
forms  needle-like  prisms. 

Calculated  for 
CisHiyOsN?:  Found: 

N 27.13  27.13 

i ,2-Dimeihylguanidin  Picrate,  C3H9N3.C6H3O7N3. — One  gram 
of  i-methyl-2-ethylpseudothiourea  hydrobromide  was  treated 
with  an  excess  of  strong  aqueous  methylamine  solution.  The 
picrate  formed  yellow  prisms  with  uneven  striated  faces.  It 
melted  to  a  clear  oil  at  178°. 

Calculated'for 
C9Hi2O7N6:  Found: 

N 26.58  26.58 

A  portion  of  the  guanidin  solution  was  precipitated  with  picro- 
lonic acid.  This  precipitate  crystallized  from  water  in  thin, 
yellow  plates  which  melted  at  262°.  It  agreed  with  the  descrip- 
tion given  by  Schenck2  who  gives  the  melting  point  26o°-262°. 
This  also  confirms  the  conclusion  of  Kutscher  and  Lohmann  that 
the  dimethyl  guanidin  from  urine  has  the  isomeric  structure. 

In  preparing  guanidins  by  the  above  method  an  excess  of 
amine  must  be  used  and  the  solutions  should  be  strong,  in  order 
to  bring  about  a  complete  reaction.  Otherwise  unaltered  pseudo- 
thiourea  will  be  precipitated  as  picrate  or  picrolonate. 

1  Zeitschr.  f.  physiol.  Chem.,  xlviii,  p.  423,  1906. 


Henry  L.  Wheeler  and  George  S.  Jamieson    117 

2-Ethylpseudothiourea  Picrate,  C3H8N2S.C6H3O7N3,  separates 
from  aqueous  solutions  in  flat,  yellow  prisms  which  melt  at  184° 
to  a  clear  oil. 

Calculated  for 
CaHnOyNsS:  Found: 

N 21.02  21.00 

2-Ethylpseudothiourea  Picrolonate,  C3H8N2S.C10H8O5N4,  forms 
difficultly  soluble,  flat,  yellow  prisms  which  melt  at  225°. 

Calculated  for 

CuH^OsNoS:  Found: 

N 22.82  22.69 

i-Methyl-2-ethylpseudothiourea  forms  a  picrate  which  crys- 
tallizes in  yellow  prisms  and  melts  to  a  clear  oil  at  157°. 


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Ber.  8,  1291. 

1876. 

N.  Menschutkin,  Tartronaminsaure.  Ber.  9,  1030.  Centr. 
B.  1876,  627. 

J.  Murdoch  und  O.  Doebner,  Ueber  Hydurilsaure.  Ber. 
9,  1102.  Centr.  B.  1876,644. 

L.  Medicus,  Spaltung  der  Uroxansaure.  Ber.  9,  1162. 
Centr.  B.  1876,  709. 

N.  Menschutkin,  Ueber  die  Zusammensetzung  der 
dialursauren  Salze.  Ann.  182,  70.  Centr.  B.  1876,  708.  Tar- 
tronaminsaure. Ann.  182,  82.  Centr.  B.  1876,  708. 

1877. 

E.  Grimaux,  Recherches  synthetiques  sur  la  serie  urique. 
Ann.  chim.  phys.  (5)  11,  356.  Centr.  B.  1877,  612. 

1878. 

E.  Mulder,  Synthese  des  cyanacetylurees  et  de  la  murexo- 
ine.  Bull.  soc.  chim.  29,  531.  Centr.  B.  1878,  612. 

E.  Grimaux,  Synthese  des  derives  uriques  de  la  serie  de 
1'alloxane.  Compt.  rend.  87,  752.  Centr.  B.  1879,  4. 

1879. 

E.  Grimaux,  Synthese  des  derives  uriques  de  la  serie  de 
1'alloxane.  Compt.  rend.  88,  85.  Bull.  soc.  chim.  31,  146.  Ber. 
11,  378.  Centr.  B.  1879,  212. 

E.  Grimaux,  Sur  1'acide  pseudo-urique.  Bull.  soc.  chim. 
31,  535. 

E.  Mulder,  Ureide,  Synthese  von  Dimethylbarbitursaure. 
Ber.  12,  465.  Centr.  B.  1879,  340.  - 

1880. 

C.  F.  Mabery  und  H.  B.  Hill,  Ueber  die  Oxydationspro- 
dukte  der  Dimethylharnsaure.  Ber.  13,  739.  Centr.  B.  1880, 
342. 

1881. 

E.  Mulder,  Einwirkung  von  Brom  auf  Uramil.  Ber.  14, 
1060.  Centr.  B.  1881,  424. 

M.  Conrad  und  M.  Guthzeit,  Ueber  Barbitursaure.  Ber. 
14,  1643.  Centr.  B.  1881,  627. 

1882. 

M.  Nencki  und  N.  Sieber,  Ueber  zwei  neue  Derivate  des 
Sulfoharnstoffs.  Jour.  p.  Chem.  25,  72.  Centr.  8.  1882,  219. 

R.  Maly  und  R.  Andreasch,  Studien  iiber  Caffein  und 
Theobromin.  Monats.  3,  92.  Centr.  B.  1882,  393. 


6  BIBLIOGRAPHY 

R.  Andreasch,  Ueber  gemischte  Alloxantine.  Monats.  3, 
428.  Centr.  B.  1882,  634. 

R.  Andreasch,  Ueber  Cyamidamalinsaure.  Monats.  3,  433. 
Centr.  B.  1882,  635. 

M.  Conrad  und  M.  Guthzeit,  Ueber  Barbitursaure.  Ber. 
15,  2844.  Centr.  B.  1883,  178. 

1883. 

R.  Behrend,  Ueber  die  Einwirkung  von  Harnstoff  auf 
Acetessigather  (Vorlaufige  Mittheilung).  Ber.  16,  3027. 

E.  Fischer  und  L.  Reese,  Cafrein,  Xanthin  und  Guanin. 
Ann.  221,  336. 

E.  von  Meyer,  Zur  Kenntniss  des  Kyanmethins.  J.  prakt. 
Chem.  27,  152.  Centr.  B.  1883,  343. 

1884. 

E.  Schilling,  Ueber  Caffeinmethylhydroxid.  Zeit.  Natur- 
wissensch.  (4)  3,  207.  Centr.  B.  1884,  811. 

A.  Pinner,  Ueber  die  Einwirkung  von  Acetessigather  auf 
die  Amidine  (Vorlaufige  Mittheilung).  Ber.  17,  2519. 

R.  Behrend,  Ueber  einige  des  Harnstoff s.    Ber.  17,  2846. 

1885. 

R.  Behrend,  Versuche  zur  Synthese  von  Korpern  der 
Harnsaurereihe.  Ann.  229,  1.  Centr.  B.  1885,  679. 

G.  Ciamician  und  P.  Magnaghi,  Ueber  die  Einwirkung  von 
Phosphorpentachlorid  auf  Alloxan.  Ber.  18,  3444. 

Ibid.  Versuche  zur  Synthese  von  Korpern  der  Harn- 
saurereihe. Ann.  231,  248.  Centr.  B.  1886,  123. 

A.  Pinner,  Ueber  die  Einwirkung  von  Acetessigather  auf 
die  Amidine.  Pyrimidine.  Ber.  18,  759;  18,  2845. 

1886. 

R.  Behrend,  Ueber  das  Verhalten  von  substituirten  Harn- 
stoff en  gegen  Acetessigather.  Ann.  233,  1.  Centr.  B.  1886, 
453. 

1887. 

R.  List,  Zur  Constitution  von  Thioharnstoff  und  Acetessig- 
ather. Ann.  236,  1.  Centr.  B.  1887,  1,  83. 

A.  Kohler,  Ueber  Nitroderivate  des  Methyluracils.  Ann. 
236,  32.  Centr.  B.  1887,  I,  58. 

R.  Behrend,  Ueber  eine  neue  Bildungsweise  der  Dibrom- 
und  Dichlorbarbitursaure.  Ann.  236,  57.  Centr.  B.  1887, 
I,  85. 

N.  Kowalewsky,  Einwirkung  des  Alloxantins  auf  das  Blut. 
Med.  Centr.  B.  25,  658.  Centr.  B.  1887,  II,  1296. 

R.  Behrend,  Versuche  zur  Synthese  von  Korpern  der 
Harnsaurereihe.  Ann.  240,  1.  Centr.  B.  1887,  II,  1311. 


BIBLIOGRAPHY  7 

G.  Pellizzari,  Verbindungen  des  Alloxans  mit  den  aromat- 
ischen  Aminen.  L.  Orosi.  10,  295.  Centr.  B.  1887,  II,  1396. 

M.  Wernecke,  Beitrage  zur  Kenntnis  des  Caffeins  und 
Caffeidins.  (Inaug.  Dissertat.  Marburg).  1887,  1.  Centr.  B. 
1887,  II,  1084. 

G.  Pellizzari,  Oxydierende  Wirkung  des  Alloxans  auf 
einige  Organische  Substanzen.  L.  Orosi.  10,  217.  Centr.  B. 
1887,  II,  1162. 

Ibid.  Verbindungen  des  Alloxans  mit  den  aromatischen 
Aminen.  L.  Orosi.  10,  253.  Centr.  B.  1887,  II,  1288. 

A.  Pinner,  Ueber  Pyrimidine.  Ber.  20,  2361.  Centr.  B. 
1887,  1289. 

A.  Michael,  Preliminary  Notes  (Malonylguanidine). 
Amer.  Chem.  Jour.  9,  219. 

1888. 

M.  Hagen,  Ueber  dimethylirtes  Methyluracil.  Ann.  244, 
1.  Centr.  B.  1888,  I,  517. 

R.  Behrend  und  O.  Roosen,  Ueber  synthetische  Versuche 
in  der  Harnsaurereihe  (Vorlaufige  Mittheilung).  Ber.  21,  999. 
Centr.  B.  1888,  I,  546. 

R.  Behrend,  Ueber  ein  Diazoderivat  des  Methyluracils. 
Ann.  245,  213.  Centr.  B.  1888,  I,  832. 

G.  Clock,  Ueber  p-Tolenylimidoather.  Ber.  21,  2650. 
Centr.  B.  1888,  II,  1333. 

Ibid.  Ueber  Phenylen-/>-diacetimidoather.  Ber.  21,  2659. 
Centr.  B.  1888,  II,  1334. 

G.  Pellizzari,  Alloxandisulfite  organischer  Basen.  L. 
Orosi.  11,  253.  Centr.  B.  1888,  II,  1546. 

Ibid.  Verbindungen  des  Alloxans  mit  den  Pyrazolbasen. 
Gaz.  18,  340.  Centr.  B.  1889,  I,  16. 

Ibid.  Alloxandisulfite  organisches  Basen.  Gas.  18,  329. 
Centr.  B.  1889,  1,  19. 

1889. 

E.  von  Meyer,  Chemische  Constitution  des  Kyanathins 
und  ahnl;cher  Verbindungen.  J.  prakt.  Chem.  39,  156.  Centr. 
B.  1889,  I,  373. 

R.  Holtzwart,  Beitrage  zur  Kenntniss  der  Polymerisation 
von  Nitrilen  Ueber  dimolekulares  Cyanmethyl.  J.  prakt.  Chem. 
39,  230.  Centr.  B.  1889,  I,  623. 

R.  Wache,  Ueber  die  Polymerisation  einiger  Nitrile.  J. 
prakt.  Chem.  39,  245.  Centr.  B.  1889,  I,  624.. 

E.  von  Meyer,  Chemische  Constitution  des  Kyanathins 
nebst  Beitragen  zur  Kenntniss  derselben  und  seiner  Abkom- 
linge.  J.  prakt.  Chem.  39,  262.  Centr.  B.  1889,  I,  625. 


8  BIBLIOGRAPHY 

G.  Pellizzari,  Alloxan  und  Pyrazolbasen.  Ann.  di  Chim. 
e.  di  Farmacologia,  9,  273.  Centr.  B.  1889,  II,  329. 

R.  Behrend,  J.  Hoffmann  und  M.  Lehmann,  Ueber  Alkyl- 
derivate  des  Methyluracils  und  des  Nitrouracils.  Ann.  253, 
65.  Centr.  B.  1889,  II,  648. 

A.  Pinner,  Ueber  Amidine  und  Pyrimidine.  Ber.  22,  1600. 
Centr.  B.  1889,  II,  655. 

Ibid.  Ueber  Pyrimidine.  Ber.  22,  1612.  Centr.  B.  1889, 
II,  655. 

E.  von  Meyer,  Notiz  iiber  Oxymiazine  (Oxypyrimidine). 
J.  prakt.  Chem.  40,  303.  Centr.  B.  1889,  II,  876. 

A.  Pinner,  Ueber  Pyrimidine.     Ber.  22,  2609.     Centr.  B. 

1889,  II,  975. 

1890. 

A.  Pinner,  Ueber  die  Einwirkung  von  Benzamidin  auf 
Acetylmalonsaureather.  Ber.  23,  161.  Centr.  B.  1890,  I,  476. 

Fausto  und  Leone  Sestini,  Uber  die  ammoniakalische 
Gaming  der  Harnsaure.  Gaz.  20,  133.  Centr.  B.  1890,  I,  1064. 

S.  Hoogewerf  et  W.  A.  Van  Dorp,  Sur  1'action  de  1'hypo- 
bromite  de  potassium  sur  la  succinphenylamide.  Rec.  d.  Trav. 
Chim.  9,  33.  Centr.  B.  1890,  II,  143. 

R.  Schwaize,  Beitrage  zur  Kenntniss  der  Polymerisation 
von  Nitrilen.  J.  prakt.  Chem.  (2)  42,  1.  Centr.  B.  1890,  II, 
336. 

R.  Behrend  und  P.  Ernert,  Ueber  Diazouracilcarbonsaure 
und  deren  Derivate.  Ann.  258,  347.  Centr.  B.  1890,  II,  507. 

Ibid.  Ueber  die  Condensation  von  Harnstoff  und  Acetessi- 
gather.  Ann.  258,  360.  Centr.  B.  1890,  II,  509. 

A.  Pinner,  Ueber  die  Einwirkung  von  Benzamidin  auf 
aromatische  Orthooxysaureather.  Ber.  23,  2934.  Centr.  B. 

1890,  II,  693. 

Ibid.  Ueber  Imidoather.  Ber.  23,  2942.  Centr.  B.  1890, 
II,  695. 

E.  Pinner  und  F.  Eschbaum.  Uber  Imidoather  des  Milch- 
saure  und  des  Mandelsaurenitrile.  Ber.  23,  2947.  Centr.  B. 
1890,  II,  695. 

E.  Pinner  und  P.  Eberhardt,  Ueber  Imidoather  aus  Ortho- 
und  Paraoxyathylbenzonitril.  Centr.  B.  1890,  II,  695. 

A.  Pinner,  Uber  die  Umwandlung  der  Nitrile  in  Imido- 
ather. Ber.  23,  2917.  Centr.  B.  1890,  II,  696. 

A.  Pinner  und  R.  Dietz,  Uber  Imidoather  des  Trimethyl- 
encyanids.  Centr.  B.  1890,  694. 

E.  Schmidt  und  M.  Wernecke,  Uber  das  Caffeidin.  Archiv. 
Pharm.  228,  516.  Centr.  B.  1890,  II,  817. 

T.  Curatolo,  Methylguanicil  und  Trimethylguanicil.  Gaz. 
20,  585.  Centr.  B.  1890,  II,  950. 


BIBLIOGRAPHY  9 

A.  Pinner.  Notizen  iiber  Imidoather  und  deren  Derivate. 
Ber.  23,  3820.  Centr.  B.  1891,  I,  318. 

1891. 

G.  Pellizzari,  Anilguanidin.    Centr.  B.  1891,  I,  659. 

J.  Jaeger,  Uber  die  Condensation  von  Guanidin  mit 
5-Ketonsaureestern.  Ann.  262,  365.  Centr.  B.  1891,  I,  787. 

O.  Kuhlung,  Ueber  die  Hydrazone  des  Alloxans  und  seiner 
Substitutionsproducte.  Ber.  24,  4140.  Centr.  B.  1892,  I,  286. 

1892. 

A.  Fock,  Krystallographische — chemische  Untersuchun- 
gen.  Zeit.  Kryst.  20,  332.  Centr.  B.  1892,  II,  351. 

1893. 

C.  Matignin,  Ureides  polybasiques  et  acide  urique.  Ann. 
chim.  phys.  (6)  28,  289.  Centr.  B.  1893,  I,  692. 

A.  Pinner,  Ueber  Saurestoffreie  Pyrimidine.  Ber.  26, 
2122.  Centr.  B.  1893,  II,  811. 

F.  Lengfeld  and  J.  Stieglitz,  Derivatives  of  Nitrogen 
Halogen  Compounds.  Amer.  Chem.  J.  15,  221. 

Ibid.     (Second  paper).     Amer.  Chem.  J.  15,  517. 

W.  Traube,  Ueber  Guanidinderivative  zweibasicher 
Sauren.  Ber.  26,  2551.  Centr.  B.  1894,  I,  23. 

A.  Kossell  und  A.  Neumann,  Ueber  das  Thymin  ein  Spal- 
tungsproduct  der  Nucleinsaure.  Ber.  26,  2753.  Centr.  B. 
1894,  I,  40. 

1894. 

W.  Traube,  Ueber  Harnstoffderivate  des  Diacetonamins. 
Ber.  27,  277.  Centr.  B.  1894,  I,  493. 

A.  Kossel  und  A.  Neumann,  Nucleinsauren.  Du  Bois- 
Reymond's  Arch.  1894,  194.  Centr.  B.  1894,  I,  1158. 

A.  Kossel  und  A.  Neumann,  Darstellung  und  Spaltungs- 
producte  der  Nucleinsaure  (Adenylsaure).  Ber.  27,  2215. 
Centr.  B.  194,  II,  708. 

A.  Angeli  Einwirkung  der  salpetrigen  Saure  auf 
Aminouracil  und  auf  Aminoaceton.  Gaz.  24,  2,  366.  Cer.  R. 

1894,  894.     Centr.  B.  1894,  II,  775. 

W.  Techow,  Ueber  die  Verwandlungen  des  Dimethylallox- 
ans.  Ber.  27,  3082.  Centr.  B.  195,  I,  30. 

1895. 

R.  Andreasch,  Ueber  Dimethylviolursaure  und  Dimethyl- 
dilitursaure.  Monats.  16,  17.  Centr.  B.  1895,  I,  842. 

A.  Pinner.  Ueber  Imidoather.     Ber.  28,  473.     Centr.  B. 

1895,  I,  880. 

R.  Andreasch,  Ueber  Dimethylviolursaure  und  Dimethyl- 
dilitursaure.  Monats.  16,  773.  Centr.  B.  1895,  II,  920. 


10  BIBLIOGRAPHY 

H.  Weidel  und  L.  Niemilowiez,  Uber  die  Bildung  von 
Thiazolderivaten  aus  Harnsaure.  Monats.  16,  721.  Centr. 
B.  1895,  II,  923. 

E.  Fischer  und  L.  Ach,  Ueber  einige  schwefelhaltige 
Verbindungen  der  Harnsauregruppe.  Ann.  288,  157.  Centr. 
B.  1895,  II,  1046. 

1896. 

H.  Ritthausen,  Wassergehalt  und  Reaction  cles  Alloxan- 
tins.  Ber.  29,  892.  Centr.  B.  1896,  I,  992. 

Ibid.  Ueber  Alloxantin  als  spaltungsproduct  des  con- 
vicins  aus  Saubohnen  (Vicia  Faba  minor)  und  Wicken  (Vicia 
sativa).  Ber.  29,  894.  Centr.  B.  1896,  I,  993. 

A.  Kossel,  Ueber  die  Bildung  von  Thymin  aus  Fisch- 
sperma.  Zeit.  physiol.  Chem.  22,  188.  Centr.  B.  1896,  II,  386. 

H.  Weidel  und  E.  Roithner,  Ueber  den  Abbau  einiger 
Saureamide  (5-Lactylharnstoff).  Monats.  17,  174. 

W.  Van  Dam,  De  1'action  des  hypobromites  alcalins  sur 
la  succindiamide.  Rec.  trav.  chim.  15,  101.  Centr.  B.  1896, 
II,  587. 

H.  Ritthausen,  Reactionen  des  Alloxantins  aus  convicin 
der  Saubohnen  und  Wicken.  Ber.  29,  2106.  Centr.  B.  1896, 
II,  27. 

1897. 

S.  Ruhemann,  Ueber  die  Bildung  der  Pyrimidone.  Ber. 
30,  821.  Centr.  B.  1897,  I,  1047. 

A.  F.  Holleman,  Sur  les  acides  nitrobarbiturique  et 
dimethylnitrobarbiturique.  Rec.  trav.  chim.  16,  162.  Centr. 
B.  1897,  II,  266. 

S.  Ruhemann  und  A.  S.  Hemmy,  Zur  Kenntniss  der 
Pyrimidine.  Ber.  30,  1488.  Centr.  B.  1897,  II,  309. 

R.  Miiller,  Ueber  die  condensation  von  Guanidin  und 
Harnstoff  mit  Oxalessigester.  J.  prakt.  Chem.  (2)  55,  505. 
Centr.  B.  1897,  II,  478. 

K.  Sembritzki,  Ueber  Malonyldiathylharnstoff  und  1,  3- 
Diathylharnsaure.  Ber.  30,  1814  Centr.  B.  1897,  II,  735. 

W.  Schacht,  Aethylen-und  Trimethylenharnstoff.  Inaug. 
Diss.  1897,  Marburg.  Centr.  B.  1897,  II,  195.  Arch.  Pharm. 
235,  441.  Centr.  B.  1897,  II,  736. 

E.  Schmidt,  Notiz  iiber  einige  Schwefelharnstoffe.  Arch. 
Pharm.  235,  435.  Centr.  B.  1897,  II,  737. 

P.  Flatow,  Ueber  Cumenylimidoather.  Ber.  30,  2006. 
Centr.  B.  1897,  II,  756. 

E.  Fischer,  Neue  Synthese  der  Harnsaure  des  Hydroxy- 
caffeins  und  des  Aminoclioxypurins.  Ber.  30,  559. 


BIBLIOGRAPHY  11 

S.  Ruhemann  und  A.  Hemmy,  Weitere  Studien  uber  den 
Dicarboxylglutaconsaureester.  Ber.  30,  2022.  Centr.  B.  1897, 
II,  861. 

P.  Fritsch,  Ueber  die  Umwandlung  des  Pentachloracetons 
in  Trichloracrylsaure  und  Monochlormalonsaure.  Ann.  297, 
312.  Centr.  B.  1897,  II,  969. 

O.  Bromberg,  Uber  die  Verbindungen  des  Alloxans  und 
Dimethylalloxans  mit  dem  Semicarbazid.  Ber.  30,  131. 

Wolf  v.  Loeben,  Ueber  s-Methylharnsaure.    Ann  298,  181. 

E.  Fischer  und  H.  Clemm,  Ueber  1-methyl  und  1,  7- 
Dimethyl-Harnsaure.  Ber.  30,  3089. 

M.  Frankel,  Ueber  Trimethylen-p-tolydiamin  und  y- 
lodpropylamin.  Ber.  30,  2947.  Centr.  B.  1897,  II,  1144. 

R.  Miiller,  Einwirkung  von  Oxalessigester  auf  Guanidin 
und  Harnstoffabkommlinge.  J.  prakt.  Chem.  56,  475. 

1898. 

D.  Vitali,  Einige  Beobachtungen  uber  die  Harnsaure  und 
iiber  die  Murexid  reaktion.    Boll.  chim.  Farm.  37,  65.    Centr. 
B.  1898,  I,  665. 

E.  Schmidt,  Ueber  PseudoharnstofFe.     Arch.  d.  Pharm. 
236,  441.    Centr.  B.  1898,  II,  765. 

O.  Kiihling.  Ueber  die  Darstellung  von  Alloxanphenyl- 
hydrazon  aus  Barbitursaure.  Ber.  31,  2110.  Centr.  B.  1898, 
II,  781. 

H.  L.  Wheeler,  Researches  on  the  Cycloamidines :  Pyrimi- 
dine  Derivatives.  Amer.  Chem.  Jour.  20,  481.  Centr.  B. 
1898,  II,  292. 

1899. 

S.  Gabriel  und  J.  Colman,  Ueber  das  Pyrimidin.  Ber. 
32,  1525.  Centr.  B.  199,  II,  108. 

W.  Gulewitsch,  Ueber  das  Arginin.  Zeit.  physiol.  Chem. 
27,  180. 

Ibid.  Ueber  das  Thymin.  Zeit.  physiol.  Chem.  27,  292. 
Centr.  B.  199,  II,  259. 

J.  Guinchard,  Ueber  die  farbigen  Salze  aus  Violursaure 
und  anderen  ring  formigen  Oximidoketonen.  Ber.  32,  1723. 
Centr.  B.  1899,  II,  290. 

S.  Gabriel  und  J.  Colman,  Zur  Kenntnis  der  Abkomm- 
linge  des  4-Methylpyrimidins.  Ber.  32,  2921.  Centr.  B.  1899, 
II,  1103. 

M.  Scholtz,  Sterische  Hinderung  chemischer  Reaktionen. 
Ber.  32,  2251.  Centr.  B.  1899,  II,  708.  (N,  N-Diphenylhexa- 
hydropyrimidine) . 

R.  Behrend  und  R.  Griinwald,  Ueber  Aminouracil.  Ann. 
309,  254.  Centr.  B.  1900,  I,  21. 


12     .  BIBLIOGRAPHY 

R.  Behrend  und  E.  Dietrich,  Ann.  309,  260.  Centr.  B. 
1900,  I,  21. 

W.  Traube  und  H.  Lorenz,  Ueber  Harnstoff  und  Thio- 
harnstoffderivate  des  Diacetonamins.  Ber.  32,  3156.  Centr. 
B.  1900,  I,  26. 

W.  Traube  und  M.  Schall,  Ueber  Harnstoff  und  Guan- 
idinderivate  des  Diacetonamins.  Ber.  32,  3174.  Centr.  B. 
1900,  I,  27. 

W.  Traube  und  R.  Schwarz,  Ueber  die  Einwirkung  von 
Amidinen  auf  Mesityloxyd  und  Phoron.  Ber.  32,  3163.  Centr. 
B.  1900,  I,  29. 

1900. 

W.  Jones,  Ueber  das  Thymin.  Z.  physiol.  Chem.  29,  20. 
Centr.  B.  1900,  I,  285. 

R.  Behrend  und  F.  C.  Meyer  Ueber  die  Einwirkung 
von  Phenylisocyanat  auf  Aminocrotonsaureester.  Ber.  33,  621. 
Centr.  B.  1900,  I,  760. 

E.  Fischer,  Ueber  aromatische  Derivate  der  Harnsaure. 
Sitzungsber.  Berliner  Akad.  Wiss.  Berlin  1900,  122.  Ber.  33, 
701.  Centr.  B.  1900,  I,  806.  (Uramil). 

H.  Steudel  und  A.  Kossel,  Ueber  das  Thymin.  Z.  physiol. 
Chem.  29,  303.  Centr.  B.  1900,  I,  967. 

W.  Traube,  Ueber  eine  neue  Synthese  des  Guanins  und 
Xanthins.  Ber.  33,  1371.  Centr.  B.  1900,  I,  1273. 

R.  Andreasch,  Ueber  Methylviolursaure  und  Methyl- 
dilitursaure.  Monats.  21,  281.  Centr.  B.  1900,  II,  41. 

S.  Ruhemann  and  H.  E.  Stapleton,  Condensation  of  Ethyl 
Acetylenedicarboxylate  with  Bases  and  5-Ketonic  Esters. 
Proc.  Chem.  Soc.  16,  121.  J.  Chem.  Soc.  77,  804.  Centr.  B. 
1900,  II,  92,  477. 

W.  Jones,  Ueber  die  Darstellung  des  Thymins.  Z.  physiol. 
Chem.  29,  461.  Centr.  B.  1900,  II,  487. 

^  H.    Steudel,   Ueber  die   constitution   des   Thymins.       Z. 
physiol.  Chem.  30,  539.    Centr.  B.  1900,  II,  1152. 

W.  Traube,  Der  synthetische  Aufbau  der  Harnsaure,  des 
Xanthins,  Theobromins  Theophyllins  und  Caffeins  aus  der 
Cyanessigsaure.  Ber.  33,  3035.  Centr.  B.  1900,  II,  1207. 

J.  Tafel  und  A.  Weinschenk,  Elektrolytische  Reduction 
des  Methyluracils.  Ber.  33,  3378.  Centr.  B.  1901,  I,  100. 

Ibid.  Elektrolytische  Reduction  von  Barbitursaure.  Ber. 
33,  3383.  Centr.  B.  1901,  I,  101. 

A.  Ascoli,  Ueber  ein  neues  Spaltungsprodukt  des  Hefe- 
nucleins.  Z.  physiol.  Chem.  31,  161.  Centr.  B.  1901,  I,  127. 
(Discovery  of  Uracil). 

S.  Gabriel,  Pyrimidin  aus  Barbitursaure.  Ber.  33,  3666. 
Centr.  B.  1901,  I,  378. 


BIBLIOGRAPHY  13 

H.    Steudel,   Ueber   die   Constitution   des    Thymins.      Z. 

physiol.  Chem.  30,  539.    Centr.  B.  1901,  I,  443;  1900,  II,  1152. 

E.  F.  Armstrong,  Uber  9-Athylharnsaure.    Ber.  33,  2308. 

1901. 

J.  Tafel,  Notiz  iiber  Hydrouracil.  Ber.  34,  144.  Centr. 
B.  1901,  I,  508. 

P.  Koech  (Behrend),  Ueber  Umwandlung  der  Isodialur- 
saure  in  Dialursaure.  Ann.  315,  246.  Centr.  B.  1901,  I,  682. 

C.  v.  Vogel  (Behrend),  Ueber  die  Condensation  von 
Isodialursaure  mit  Thioharnstorf.  Ann.  315,  259.  Centr.  B. 
1901,  I,  682. 

-E.  Fischer  und  G.  Roeder,  Synthese  des  Thymins  und 
anderer  Uracile.  Sitzung.  Kgl.  Akad.  Wiss.  Berlin  1901,  12; 
268.  Centr.  B.  1901,  I,  887. 

H.  Steudel,  Das  Verhalten  einiger  Pyrimidinderivate  im 
Organismus.  Zeit.  physiol.  Chem.  52,  285.  Centr.  B.  1901, 1, 
1235. 

S.  Gabriel  und  J.  Colman,  Synthesen  in  der  Purinreihe. 
Ber.  34,  1234.  Centr.  B.  1901,  I,  1279. 

J.  Tafel,  Ueber  die  Tetrahydroharnsaure.  Ber.  34,  1181. 
Centr.  B.  1901,  I,  1287. 

A.  Weinschenk,  Ueber  Condensation  von  Barbitursaure 
mit  aromatischen  Aldehyden  zu  gefarbten  Substanzen.  Ber. 
34,  1685.  Centr.  B.  1901,  II,  281. 

T.  Rappeport,  Ueber  einige  Pyrimidine  und  Kyanidine 
aus  dem  Paranitrobenzamidin.  Ber.  34,  1983.  Centr.  B.  1901, 
II. 

G.  Pellizzari  und  C.  Roncagliolo,  Ueber  die  isomeren 
Phenylamidoguanidine.  Gaz.  31,  513.  Centr.  B.  1901,  II,  591. 

J.  Schlenker,  Ueber  4,  5-Dimethylpyrimidin.  Ber.  34, 
2812.  Centr.  B.  1901,  II,  1047. 

J.  Tafel  und  L.  Reindl,  Elektrolytische  Reduction  einiger 
cyclischer  Ureide.  Ber.  34,  3286.  Centr.  B.  1901,  II,  1154. 

S.  Gabriel,  Amidoderivate  des  Pyrimidins.  Ber.  34,  3362. 
Centr.  B.  1901,  II,  1172. 

R.  Behrend  und  H.  Schreiber,  Ueber  Brom  und  Chlor- 
aminocrotonsaureester.  Ann.  318,  371.  Centr.  B.  1901,  II, 
1334. 

E.  Fischer  und  G.  Roeder,  Synthese  des  Uracils,  Thymins 
und  Phenyluracils.  Ber.  34,  3751.  Centr.  B.  1902,  I,  53. 

St.  Augerstein,  Ueber  4,  6-Dimethylpyrimidin.  Ber.  34, 
3956.  Centr.  B.  1902,  I,  126. 

A.  Pinner,  Ueber  Pyridoylessigester.  Ber.  34,  4234. 
Centr.  B.  1902,  I,  209. 


14  BIBLIOGRAPHY 

W»  O.  Emery,  Ueber  Derivate  des  Pyrimidins.  Ber.  34, 
4178.  Centr.  B.  1902,  I,  265. 

E.  Fischer  und  G.  Roeder,  Nachtrag  zu  der  Mittheilung: 
Synthese  des  Uracils,  Thymins  und  Phenyluracils.  Ber.  34, 
4129.  Centr.  B.  1902,  I,  267. 

A.  Agrestini,  Uber  einige  Reaktionen  des  Alloxans  und 
des  Alloxantins.  Boll.  Chim.  Farm.  41,  5.  Centr.  B.  1902,  I, 
631. 

1902. 

S.  Gabriel  und  J.  Colman,  Zur  Kenntniss  der  methylirten 
Pyrimidine.  Ber.  35,  1569.  Centr.  B.  1902,  I,  1235. 

K.  F.  M.  J.  Schmidt,  Zur  Kenntniss  der  methylirten  Pyrimi- 
dine.   Ber.  35,  1575.    Centr.  B.  1902,  I,  1237. 

E.  Fischer  und  H.  Tullner,  Verwandlung  der  Isoharn- 
saure  in  Harnsaure  und  Thioxanthin.     Ber.  35,  2563.     Centr. 
B.  1902,  II,  578. 

R.  Behrend  und  R.  Thurm,  Ueber  die  Constitution  der 
Alkylderivate  des  Methyluracils  und  der  /4-Methylharnsaure. 
Ann.  323,  160.  Centr.  B.  1902,  II,  889. 

R.  Behrend  urid  R.  Griinwald,  Ueber  die  Oxydation  des 
Methyluracils.  Ann.  323,  178.  Centr.  B.  1902,  II,  890. 

G.  Wollers  (Behrend),  Ueber  Diazoisonitrosomethyluracil 
und  4-Aminopyrazol.  Ann.  323,  379.  Centr.  B.  1902,  II,  1101. 

F.  Kunckell  und  L.  Zumbusch,  Ueber  die  Einwirkung  von 
Mucobrom   und   Mucochlorsaure   auf   Benzamidin.      Ber.   35, 
3164.    Centr.  B.  1902,  II,  1215. 

F.  Kunckell  und  O.  Sarfert,  Ueber  die  Einwirkung  von 
Benzamidin  auf  5-Brom-a-Benzylacetophenon.  Ber.  35,  3169. 
Centr.  B.  1902,  II,  1216. 

F.  Sachs  und  W.  Lewin,  Zur  Kenntniss  des  />-dimethyl- 
amidobenzaldehyde.  Ber.  35,  3569.  Centr.  B.  1902,  II,  1385. 

L.  Kaess  und  J.  Gruszhiewicz,  Ueber  die  Verbindungen 
der  Mesoxalsaure  (Dioxymalonsaure)  und  Glyoxylsaure  mit 
Guanidin.  Ber.  35,  3600.  Centr.  B.  1902,  II,  1411. 

R.  Andreasch,  Zur  Kenntniss  des  Lactylharnstoffes. 
Monats.  23,  803.  Centr.  B.  1902,  II,  1416. 

1903. 

A.  Kossel  und  H.  Steudel.  Ueber  das  Vorkommen  des 
Uracils  in  Thierkorper.  Zeit.  physiol.  Chem.  37,  245.  Centr. 
B.  1903,  I,  593. 

A.  Kossel  und  H.  Steudel,  Ueber  das  Cytosin.  Zeit. 
physiol.  Chem.  37,  377.  Centr.  B.  1903,  I,  725. 

P.  A.  Levene,  Ueber  das  Vorkommen  von  Uracil  bei  der 
Pankreasautolyse.  Zeit.  physiol.  Chem.  37,  527.  Centr.  B. 
1903,  I,  1218. 


BIBLIOGRAPHY  15 

H.  L.  Wheeler  and  H.  F.  Merriam,  On  Some  Condensa- 
tion Products  of  the  Pseudothioureas :  Syntheses  of  Uracil, 
Thymine  and  Similar  Compounds.  Amer.  Chem.  Tour.  29, 
478.  Centr.  B.  1903,  I,  1308. 

H.  L.  Wheeler  and  T.  B.  Johnson,  Syntheses  of  Aminooxy- 
primidines  having  the  Composition  of  Cytosine:  2-Amino-6- 
oxypyrimidine  and  2-Oxy-6-aminopyrimidine.  Amer.  Chem. 
Jour.  29,  492.  Centr.  B.  1903,  I,  1310. 

Ibid.  On  Cytosine  or  2-Oxy-6-aminopyrimidine  from 
Tritico-nucleic  Acid.  Amer.  Chem.  Jour.  29,  505.  Centr.  B. 
1903,  I,  1311. 

A.  Kossel  und  H.  Steudel,  Weitere  Untersiichungen  iiber 
das  Cytosin.  Zeit.  physiol.  Chem.  38,  49.  Centr.  B.  1903,  I, 
365. 

P.  A.  Levene,  Darstellung  und  Analyse  einiger  Nuclein- 
sauren.  Zeit.  physiol.  Chem.  38,  80.  Centr.  B.  1903,  I,  1366. 

F.  Kutscher,  Eine  Methode  zur  Darstellung  des  Cytosins. 
Zeit.  "physiol.  Chem.  38,  170.  Centr.  B.  1903,  I,  1417. 

A.  Byk,  Ueber  einige  Derivate  des  Pyrimidins.  Ber.  36, 
1915.  Centr.  B.  1903,  II,  208. 

E.  Biittner,  Einige  Umsetzungen  des  2,  4,  6-Trichlor- 
pyrimidins.  Ber.  36,  2227.  Centr.  B.  1903,  II,  449. 

R.  Behrend  und  L.  Fricke,  Ueber  die  Oxydation  des 
Trimethyluracils.  Ann.  327,  253.  Centr.  B.  1903,  II,  349. 

S.  Gabriel  und  J.  Colman,  Zur  Kenntniss  des  Pyrimidins 
und  methylirter  Pyrimidine.  Ber.  36,  3379.  Centr.  B.  1903, 
II,  1192. 

H.  Steudel,  Futterungsversuche  in  der  Pyrimidingruppe. 
Zeit.  physiol.  Chem.  39,  136.  Centr.  B.  1903,  II,  591. 

P.  A.  Levene,  Darstellung  und  Analyse  einiger  Nuclein- 
sauren.  Zeit.  physiol.  Chem.  39,  479. 

S.  Ruhemann,  The  Action  of  Benzamidin  on  B-Diketonic 
Olefines.  Proceedings  Chem.  Soc.  (London)  19,  246.  Centr. 
B.  1904,  I,  164. 

1904. 

W.  Traube.  Der  Aufbau  der  Xanthinbasen  aus  der 
Cyanessigsaure.  Synthese  des  Hypoxanthins  und  Adenins. 
Ann.  331,  64.  Centr.  B.  1904,  I,  1199. 

W.  M.  Bruce,  On  the  Oxygen  Ethers  of  Ureas.  Jour. 
Amer.  Chem.  Soc.  26,  419.  Centr.  B.  1904,  I,  1558. 

Ibid.  Jour.  Amer.  Chem.  Soc.  26,  449.  Centr.  B.  1904, 
II,  29. 

H.  L.  Wheeler  and  T.  B.  Johnson,  5-Methylcytosine. 
Amer.  Chem.  Jour.  31,  591.  Centr.  B.  1904,  II,  240. 

M.  Slimmer  and  J.  Stieglitz,  The  Constitution  of  Purpuric 


16  BIBLIOGRAPHY 

Acid  and  of  Murexide.  Amer.  Chem.  Jour.  31,  661.  Centr. 
B.  1904,  II,  316. 

O.  Piloty,  Ueber  die  Harnsauregruppe.  Ann.  333,  22. 
Centr.  B.  1904,  II,  768. 

Ibid.    Ann.  333,  71.    Centr.  B.  1904,  II,  826. 

R.  Mohlau,  Ueber  die  Constitution  der  Purpursaure  und 
des  Murexids.  Ber.  37,  2686.  Centr.  B.  1904,  II,  829. 

T.  B.  Johnson  and  S.  H.  Clapp,  Synthesis  of  2-Amino-5- 
Methyl-6-Oxyprimidine.  Amer.  Chem.  Jour.  32,  130.  Centr. 
B.  1904,  II,  955. 

R.  Burian,  Zur  Frage  der  Bindung  der  Purinbasen  im 
Nucleinsauremolekiil.  Zeit.  physiol.  Chem.  42,  297.  Centr. 
B.  1904,  II,  996. 

E.  Fischer  und  A.  Dilthey,  Ueber  C-Dialkylbarbitur- 
sauren  und  iiber  die  Ureide  der  Dialkylessigsauren.  Ann.  335, 
334.  Centr.  B.  1904,  II,  1381. 

H.  L.  Wheeler  and  G.  S.  Jamieson,  2-Oxy-4,  6-Diamino- 
pyrimidine.  Amer.  Chem.  Jour.  32,  342.  Centr.  B.  1904,  II, 
1413. 

S.  Gabriel,  Ueber  2-Methylpyrimidin.  Ber.  37,  3638. 
Centr.  B.  1904,  II,  1415. 

S.  Gabriel  und  J.  Colman,  Zur  Darstellung  des  2,  4,  6- 
Trichlorpyrimidin.  Ber.  37,  3657.  Centr.  B.  1904,  II,  1416. 

E.  Fischer  und  A.  Dilthey,  Ueber  C-Dialkylbarbitur- 
sauren  und  iiber  die  Ureide  der  Dialkylessigsauren.  Ann.  336, 
345.  Centr.  B.  1904,  II,  1713. 

W.  Traube,  Ueber  2-Amino-Adenin.  Ber.  37,  4544. 
Centr.  B.  1905,  I,  160. 

1905. 

S.  Gabriel,  Zur  Geschichte  der  Aminopyridine  (Amino- 
pyrimidine).  Ber.  38,  149.  Centr.  B.  1905,  I,  459. 

S.  Gabriel,  Ueber  Isocystein  und  Isocystin.  Ber.  38,  630. 
Centr.  B.  1905,  I,  807. 

S.  Gabriel,  Notizen  iiber  Bromdihydrouracil.  Ber.  38, 
1689.  Centr.  B.  1905,  I,  1536. 

H.  L.  Wheeler  and  H.  S.  Bristol,  The  Structure  of  Some 
Substitution  Products.  Amer.  Chem.  Jour.  33,  437.  Centr. 
B.  1905,  I,  1709. 

Ibid.  The  Action  of  Potassium  Thiocyanate  Upon  Some 
Imide  Chlorides.  Amer.  Chem.  Jour.  33,  448.  Centr.  B.  1905, 
I,  1711. 

T.  Posner,  Zur  Kenntniss  der  B-Aminosauren.  Ber.  38, 
2316.  Centr.  B.  1905,  11,  479. 

R.   Bartling    (Behrend),   Nachtrag  zu   der  Abhandlung: 


BIBLIOGRAPHY  17 

Ueber  die  condensation  von  Isodialursaure  mit  Thioharnstoff. 
Ann.  339,  37. 

M.  Conrad,  Ueber  Iminobarbitursauren  und  Barbitur- 
sauren.  Ann.  340,  310.  Centr.  B.  1905,  II,  889. 

M.  Conrad  und  A.  Zart,  Ueber  Iminodialkylmalonylalkyl 
und  Phenylharnstorre.  Ann.  340,  326. 

Ibid.  Ueber  Cyandialkylacetylharnstoffe  und  iiber  die 
Amide  substituirter  Malonsauren  und  Cyanessigsauren.  Ann. 
340,  335.  Centr.  B.  1905,  II,  891. 

O.  Kiihling,  Ueber  condensationsproducte  des  Alloxans 
mit  gesattigten  Ketonen.  Ber.  3003.  Centr.  B.  1905,  II, 
1240. 

P.  A.  Levene,  Darstellung  und  Analyse  einiger  Nuclein- 
sauren.  Milznucleinsaure.  Zeit.  physiol.  Chem.  45,  370. 
Centr.  B.  1905,  II,  1502. 

T.  B.  Johnson  and  C.  O.  Johns,  The  Action  of  Aqueous 
and  Alcoholic  Ammonia,  and  Aniline  on  Some  Halogen  and 
Mercapto  Pyrimidines.  Amer.  Chem.  Jour.  34,  175.  Centr. 
B.  1905,  II,  1353. 

T.  B.  Johnson,  2-Ethylmercapto-5-amino-6-oxpyrimidine. 
Amer.  Chem.  Jour.  34,  191.  Centr.  B.  1905,  II,  1499. 

O.  Gerngross,  Ueber  eine  Synthese  des  Thymins.  Ber. 
38,  3408.  Centr.  B.  1905,  I,  1605. 

H.  Steudel,  Zur  Kenntniss  der  Thymusnucleinsauren. 
Zeit.  physiol.  Chem.  46,  332.  Centr.  B.  1906,  I,  142. 

W.  N.  Hartley,  The  Absorption  Spectra  of  Uric  Acid, 
Murexide  and  the  Ureides  in  Relation  to  Color  and  their 
Chemical  Structure.  Jour.  Chem.  Soc.  (London),  87,  1796. 

H.  Osten  (R.  Behrend),  Ueber  Trioxydihydromethylura- 
cil.  Ann.  343,  133.  Centr.  B.  1906,  I,  749. 

C.  Huf schmidt  (R.  Behrend),  Die  Oxydation  der  me- 
thylirten  Uracile.  Ann.  343,  155. 

Ibid.    Nitriung  des  Trimethyluracils.    Ann.  343,  168. 

A.  Einhorn,  Ueber  die  N-Methylolverbindungen  der 
Saureamide.  Ann.  343,  207. 

E.  von  Meyer,  Ueber  die  Konstitution  und  Bildungsweise 
der  Kyanalkine  genannten  trimolekularen  Nitrile.  Ber.  K. 
sachs.  Ges.  Wiss.  math.  phys.  57,  324.  Centr.  B.  1906,  I,  941. 

T.  B.  Johnson  and  C.  O.  Johns,  On  2,  5-Diamino-6-oxy- 
pyrimidine.  Am.  Chem.  Jour.  34,  554.  Centr.  B.  1906,  I. 

1906. 

O.  Isay,  Eine  synthese  des  Purins.  Ber.  39,  250.  Centr. 
B.  1906,  I,  659. 

W.  Traube  und  W.  Nithack,  Ueber  die  Einwirkung  von 


18  BIBLIOGRAPHY 

Aldehyden  auf  Orthodiamine  der  Pyrimidinreihe.  Ber.  39, 
227.  Centr.  B.  1906,  I,  687. 

R.  Behrend  und  H.  Friedrich,  Zur  Kenntnis  der  Dialur- 
saure.  Ann.  344,  1.  Centr.  B.  1906,  I,  1007. 

R.  Behrend  und  H.  Hennicke,  Ueber  die  Einwirkung  von 
Senfolen  auf  Aminocrotonsaureester.  Ann.  344,  19.  Centr. 
B.  1906,  I,  1007. 

W.  Traube  und  F.  Winter,  Synthese  des  3-Methylhypo- 
xanthins.  Arch.  d.  Pharm.  244,  11.  Centr.  B.  1906,  I,  1337. 

J.  A.  Mandel  und  P.  A.  Levene,  Darstellung  und  Analyse 
einiger  Nukleinsauren :  Uber  die  Nukleinsaure  der  Niere. 
Zeit.  physiol.  Chem.  47,  140.  Centr.  B.  1906,  I,  1363. 

T.  B.  Johnson  and  C.  O.  Johns,  Some  5-Iodopyrimidin 
Derivatives.  5-Iodocytosin.  Jour.  Biolog.  Chem.  1,  305. 
Centr.  B.  1906,  I,  1889. 

R.  Mohlau  und  H.  Litter,  Zur  Frage  der  Konstitution  des 
Murexids  und  der  Purpursaure.  Jour,  prakt.  Chem.  73,  449. 
Centr.  B.  1906,  II,  503. 

Ibid.  Ueber  die  Einwirkung  primarer  Amine  auf  Allox- 
antin.  Jour,  prakt.  Chem.  73,  472.  Centr.  B.  1906,  II,  504. 

T.  B.  Johnson  and  E.  V.  McCollum,  On  Methods  of 
Synthesizing  Isobarbituric  Acid  and  5-Oxycytosin.  Jour. 
Biolog.  Chem.  1,  437.  Centr.  B.  1906,  I,  889. 

T.  B.  Johnson  and  E.  V.  McCollum,  The  Action  of  Potas- 
sium Thiocyanate  Upon  Imide  Chlorides.  Amer.  Chem.  Jour., 
36,  136.  Centr.  B.  1906,  II,  1063. 

T.  B.  Johnson  and  E.  V.  McCollum,  On  The  Formation  of 
Purines  from  Urea  Pyrimidines.  Amer.  Chem.  Jour.  36,  149. 
Centr.  B.  1906,  II,  1064. 

T.  B.  Johnson,  C.  O.  Johns,  and  F.  W.  Heyl,  On  5-Nitro- 
cytosine  and  Its  Reduction  to  2-Oxy-5,  6-Diaminopyrimidine. 
Amer.  Chem.  Jour.  36,  160.  Centr.  B.  1906,  II,  1066  . 

T.  B.  Johnson  and  G.  A.  Menge,  5-Ethylcytosin.  Jour. 
Biolog.  Chem.  2,  105.  Centr.  B.  1906,  II,  1507.  _ 

H.  Steudel,  Ueber  die  Oxydation  der  Nucleinsaure.  Zeit 
physiol.  Chem.  48,  425. 

M.  A.  Whitely,  1,  3-Diphenylbarbituric  Acid  and  Some 
Colored  Derivatives  of  the  Same.  Synthesis  of  1,  3-Diphenyl- 
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Centr.  B.  1906,  II,  1404. 

J.  K.  Wood,  The  Acidic  Constants  of  Some  Ureides  and 
Uric  Acid  Derivatives.  Jour.  Chem.  Soc.  (London),  89,  1831. 
Centr.  B.  1907,  I,  539. 

P.  A.  Levene  und  J.  A.  Mandel,  Darstellung  und  Analyse 
einiger  Nucleinsauren.  Nucleinsaure  der  Spermatozoen  des 
Maifisches.  Zeit.  physiol.  Chem.  50,  1.  Centr.  B.  1907,  I,  354. 


BIBLIOGRAPHY  19 

J.  A.  Mandel  and  P.  A.  Levene,  On  the  Pyrimidine  Bases 
of  the  Nucleic  Acid  Obtained  from  Fish  Eggs.  Jour.  Biolog. 
Chem.  1,  425.  Centr.  B.  1906, 1,  1790. 

1907. 

H.  Burrows  and  C.  A.  Keane,  The  Condensation  of 
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don), 91,  269.  Centr.  B.  1907,  I,  1270. 

H.  L.  Wheeler,  T.  B.  Johnson  and  C.  O.  Johns,  Synthesis 
of  Uracil-5-carboxylic  Acid.  Amer.  Chem.  Jour.  37,  392. 
Centr.  B.  1907,  I,  1632. 

E.  F.  J.  Atkinson,  H.  Ingham  and  J.  F.  Thorpe,  The 
Formation  and  Reactions  of  Iminocomponds.  The  Formation 
of  1,  3-Naphthylenediamine  and  Its  Derivatives '  from  o- 
Tolunitrile.  Jour.  Chem.  Soc.  (London),  91,  583.  Centr.  B. 
1907,  II,  69. 

R.  Burian,  Weitere  Beitrage  zur  Kenntnis  der  Diazoam- 
inoverbindungen  der  Purinbasen.  Zeit.  physiol.  Chem.  51,  425. 

Ibid.  Pyrimidinderivate  aus  Purinbasen.  Ziet.  physiol. 
Chem.  51,  438.  Centr.  B.  1907,  II,  141. 

R.  Behrend  und  O.  Hoebel,  Ueber  Alkylderivate  des 
Methyluracils.  Ann.  353,  242.  Centr.  B.  1907,  II,  304. 

R.  Behrend  und  G.  Offe,  Ueber  die  Oxydation  von  Uracil- 
derivaten.  Ann.  353,  267.  Centr.  B.  1907,  II,  305. 

T.  B.  Johnson  and  F.  W.  Heyl,  Some  Condensation  Pro- 
ducts of  a  Substituted  Pseudothiourea :  Synthesis  of  1-Methyl- 
uracil.  Amer.  Chem.  Jour.  37,  628.  Centr.  B.  1907,  II,  449. 

S.  J.  M.  Auld,  Mercury  Derivatives  of  Pseudo  Acids  Con- 
taining the  Group  CONH.  Jour.  Chem.  Soc.  (London),  91, 
1045.  Centr.  B.  1907,  II,  831. 

P.  A.  Levene,  Notiz  iiber  die  Pikrolonate  einiger  Nuclein- 
basen.  Biochem.  Zeit.  4,  320.  Centr.  B.  1907,  II,  587. 

Ibid.  Ueber  die  diuretische  Wirkung  des  Thymins. 
Biochem.  Zeit.  4,  316.  Centr.  B.  1907,  II,  619;  also  Jour. 
Exper.  Medicine,  9,  229. 

W.  Gossling,  Dialkylbarbitursauren.  Chem.  Ztg.  31,  711. 
Centr.  B.  1907,  II,  689. 

M.  A.  Whiteley,  Studies  in  the  Barbituric  Acid  Series.  1, 
3-Diphenylbarbituric  Acid  and  Some  Coloured  Derivatives. 
Jour.  Chem.  Soc.  (London),  91, 1330.  Centr.  B.  1907,  II,  1065. 

H.  L.  Wheeler  and  T.  B.  Johnson,  On  a  Color  Test  for 
Uracil  and  Cytosin.  Jour.  Biolog.  Chem.  3,  183.  Centr.  1907, 
II,  1087. 

A.  P.  N.  Franchimont  and  H.  Friedmann,  L'action  de 
1'acide  azotique  reel  sur  la  trimethylene-ureine  et  sur  1'hy- 
drouracil.  Rec.  trav.  chim.  26,  218.  Centr.  B.  1907,  II,  1248. 


20  BIBLIOGRAPHY 

J.  Tafel  und  P.  A.  Houseman,  Zur  Kenntniss  des  Isopurons. 
Ber.  40,  3743.  Centr.  B.  1907,  II,  1401. 

H.  L.  Wheeler,  On  Some  Salts  of  Cytosin,  Isocytosin,  6- 
Aminopyrimidin  and  6-Oxypyrimidin.  Jour.  Biolog.  Chem.  3, 
285. 

H.  L.  Wheeler,  Uracil-4-Carboxylic  Acid.  Amer.  Chem. 
Jour.  38,  358.  Centr.  B.  1907,  II,  1634. 

T.  B.  Johnson  and  F.  W.  Heyl,  The  Action  of  Methyl 
Iodide  on  2-Anilino-6-oxypyrimidine,  and  the  Synthesis  of  2- 
Anilinoyprimidine.  Amer.  Chem.  Jour.  38,  237.  Centr.  B. 

1907,  II,  1248. 

T.  B.  Johnson,  Synthesis  of  Thymin  4-Carboxylic  Acid. 
Jour.  Biolog.  Chem.  3,  299.  Centr.  B.  1907,  II,  1531. 

H.  L.  Wheeler  and  C.  O.  Johns,  Synthesis  of  Cytosine-5- 
Carboxylic  Acid.  Amer.  Chem.  Jour.  38,  594.  Centr.  B.  1908, 
I,  289. 

T.  B.  Johnson  and  C.  F.  Speh,  Synthesis  of  Thymine-5- 
Carboxylic  Acid.  Amer.  Chem.  Jour.  38,  602.  Centr.  B.  1908, 
I,  390. 

T.  B.  Johnson  and  F.  W.  Heyl,  Synthesis  of  4-Methyl- 
uracil-5-Acetic  Acid.  Amer.  Chem.  Jour.  38,  659.  Centr.  B. 

1908,  I,  391. 

M.  Conrad,  Zur  Kenntnis  der  Hydurilsaure.  Ann.  356,  24. 
Centr.  B.  1907,  II,  1609. 

U.  Suzuki,  K.  Aso  und  H.  Mitarai,  Ueber  die  chemische 
Zusammensetzung  der  japanischen  Sojasauce  oder  Schoyu. 
Bull,  college  Agric.  Tokio,  7,  477.  Centr.  B.  1907,  II,  1649. 

J.  Tafel  und  H.  B.  Thompson,  Elektrolytische  Reduktion 
der  Aethylbarbitursauren.  Ber.  40,  4489.  Centr.  B.  1908,  I, 
122. 

H.  Steudel,  Ueber  die  Bildung  von  Pyrimidinderivate  aus 
Purinkorpern.  Zeit.  physiol.  Chem.  53,  508.  Centr.  B.  1908, 
I,  123. 

A.  Einhorn  und  H.  v.  Diesbach,  Ueber  die  Reduktion  der 
Diathylthiobarbitursaure.  Ber.  40,  4902.  Centr.  B.  1908,  I, 
455. 

H.  L.  Wheeler  and  G.  S.  Jamieson,  On  Some  Picrolonates. 
Jour.  Biolog.  Chem.  3,  111. 

1908. 

F.  Sachs  und  E.  Appenzeller,  Uber  den  Tetramethyl-2, 
4-diaminobenzaldehyde.  Ber.  41,  91.  Centr.  B.  1908,  1,^519. 

R.  Majima,  Uber  die  Kondensation  der  Alkylguanidine 
mit  Acetessigester  usw.  Ber.  41,  176.  Centr.  B.  1908,  I,  1044. 

F.  Baum,  Zur  Kenntniss  der  Traubeschen  Pyrimidin-syn- 
thesen.  Ber.  41,  532.  Centr.  B.  1908,  I,  1167. 


BIBLIOGRAPHY  21 

S.  Gabriel,  Uber  einige  synthetisch  verwerthbase  Derivate 
der  Aminosauren.  Ber.  41,  242.  Centr.  B.  1908,  I,  729. 

A.  Einhorn,  Ueber  neue  Arzneimittel.  Ann.  359,  145. 
Centr.  B.  1908,  I,  1535. 

P.  A.  Levene  und  J.  A.  Mandel,  Zur  Herkunst  des  Cytos- 
ins  beider  Hydrolyse  der  tierischen  Nucleinsauren.  Biochem. 
Zeit.  9,  233.  Centr.  B.  1908,  I,  1710. 

T.  B.  Osborne  and  F.  W.  Heyl,  The  Pyrimidine  Deriva- 
tives in  Nucleic  Acid.  Amer.  Jour,  of  Physiol.  21,  157. 

T.  de  Haan,  La  condensation  5-dicetones  avec  Turee. 
Rec.  trav.  chim.  27,  162.  Centr.  B.  1908,  II,  35. 

O.  Kuhling,  Uber  Phenacyldialursaure,  Tartronursaure 
und  Isohydantoinsaure.  Ber.  41,  1658.  Centr.  B.  1908,  II,  53. 

F.  Pohl,  Zur  Kenntniss  des  Dicyandiamids.  Jour.  pr. 
Chem  (2)  77,  533.  Centr.  B.  1908,  II,  151. 

P.  A.  Levene  und  J.  Mandel,  Uber  die  Konstitution  der 
Thymonucleinsaure.  Ber.  41,  1905.  Centr.  B.  1908,  II,  424. 

R.  Behrend  und  K.  Beer,  Uber  Trioxydihydromethyl- 
uracil.  Ann.  362,  115.  Centr.  B.  1908,  II,  886. 

T.  B.  Johnson,  A  Method  of  Separating  Thymin  from 
Uracil.  Jour.  Bilog.  Chem.  4,  407.  Centr.  B.  1908,  II,  1043. 

T.  B.  Johnson,  The  Action  of  Nitric  Acid  on  2,  6-Dioxy- 
pyrimidines.  Oxynitrohydrothymine.  Amer.  Chem.  Jour.  40, 
19.  Centr.  B.  1908,  II,  802. 

L.  Hugouneng  et  A.  Morel,  Contribution  a  1'etude  de  la 
constitution  des  nucleoproteides.  Recherches  sur  les  consti- 
tuants  de  la  pepsine.  Compt.  rend.  147,  212.  Centr.  B.  1908, 
II,  805. 

H.  L.  Wheeler  and  L.  M.  Liddle,  Synthesis  of  Uracil-3- 
acetic  Acid.  Jour.  Amer.  Chem.  Soc.  30,  1152.  Centr.  B.  1908, 
II,  1045. 

Ibid:  Synthesis  of  Uracil-4-acetic  Acid.  Jour.  Amer. 
Chem.  Soc.  30,  1156.  Centr.  B.  1908,  II,  1045. 

T.  B.  Johnson  and  S.  H.  Clapp,  Syntheses  of  Some  Nitro- 
gen-Alkyl  Derivatives  of  Cytosine,  Thymine  and  Uracil.  Jour. 
Biolog.  Chem.  5,  49.  Centr.  B.  1908,  II,  1264. 

T.  B.  Johnson  and  S.  H.  Clapp,  The  Action  of  Diazo- 
Benzene  Sulphonic  Acid  on  Thymin,  Uracil  and  Cytosin. 
Jour.  Biolog.  Chem.  5,  163.  Centr.  B.  1908,  II,  1872. 

J.  Mandel,  Jacobs  and  P.  Levene,  On  Nucleic  Acids. 
Proceedings  Soc.  Exp.  Biolog.  Med.  5,  92. 

T.  B.  Johnson  and  W.  F.  Storey,  The  Action  of  Potassium 
Thiocyanate  Upon  Some  Imide-Chlorides.  Amer.  Chem. 
Jour.  40,  131.  Centr.  B.  1908,  II,  1105. 


22  BIBLIOGRAPHY 

E.  L.      Pinner,      Uber      2-Phenyl-4,6-dioxypyrimidine, 
Malonylbenzamidine.    Ber.  41,  3517.    Centr.  B.  1908,  II,  1692. 

H.  L.  Wheeler  and  C.  O.  Johns,  Synthesis  of  Cytosine- 
5-Carboxamide.  Amer.  Chem.  Jour.  40,  234.  Centr.  B.  1908, 
II,  1781. 

C.  O.  Johns,  Synthesis  of  4-Methylcytosine.  Amer.  Chem. 
Jour.  40,  348.  Centr.  B.  1908,  II,  1933. 

T.  B.  Johnson  and  J.  H.  Derby,  Jr.,  Syntheses  of  Some 
Benzyl  Derivatives  of  Uracil  and  Thymine.  Amer.  Chem. 
jour.  40,  444.  Centr.  B.  1909,  I,  85. 

F.  Sachs  und  G.  Meyerheim,  Uber  Azinpurine.     Ber.  41, 
3957.    Centr.  B.  1909,  I,  31. 

T.  B.  Johnson  and  D.  B.  Jones,  Synthesis  of  new  Deriva- 
tives of  5-Hydroxyuracil  (Isobarbituric  Acid).  Amer.  Chem. 
Jour.  40,  538.  Centr.  B.  1909,  I,  193. 

H.  L.  Wheeler  and  L.  M.  Liddle,  Thio  Derivatives  of 
Uracil  and  the  Preparation  of  Uracil  in  Quantity.  Amer. 
Chem.  Jour.  40,  547.  Centr.  B.  1909,  I,  447. 

1909. 

M.  Engelmann,  Uber  eine  Synthese  des  1-Methylxanthins. 
Ber.  42,  177.  Centr.  B.  1909,  I,  524,  806. 

A.  Guyot  et  E.  Michel,  Condensation  des  ethers  mes- 
oxaliques  avec  les  amines  aromatique  tertiaires.  Compt.  rend. 
148,  229. 

C.  O.  Johns,  On  the  Formation  of  Purine  Derivatives 
from  4-Methyl  Cytosine.  Amer.  Chem.  Jour.  41,  58.,  Centr. 
B.  1909,  I,  925. 

M.  Conrad  und  A.  Schulze,  Uber  Malonylamidderivate. 
Ber.  42,  729.  Centr.  B.  1909,  I,  1087. 

O.  Stark,  Zur  Konstitution  des  Acetylacetonharnstoffs 
(4,  6-Dimethyl-2-ketopyrimidin).  Kondensation  mit  aroma- 
tischen  Aldehyden.  Ber.  42,  699.  Centr.  B.  1909,  I,  1243.  ^ 

Ibid:  Zur  Konstitution  des  Acetylacetonharnstoffs.  Ein- 
wirkung  von  Brom  auf  Acetylacetonharnstoff  und  seine  Kon- 
densationsprodukte  mit  Aldehyden.  Ber.  42,  708.  Centr.  B. 
1909,  I,  1245. 

E.  Fourneau,  Sur  les  acides  oxyamines.  Derives  amines 
de  1'acide  oxyisobutyrique.  Bull.  soc.  chim.  (4)  5,  229.  Centr. 
B.  1909,  I,  1318  (Hydrothymin). 

A.  Hantzsch,  Uber  Pantochromie  und  Chromoisomerie 
von  Violuraten  und  verwandten  Oximinoketonsalzen.  Ber. 
42,  966.  Centr.  B.  1909,  I,  1390. 

A.  Hantzsch  und  B.  Issaias,  Uber  polychrome  und 
Ester  der  Violursauregruppe.  Ber.  42,  986.  Centr.  B.  1909, 
I,  1393. 


BIBLIOGRAPHY  23 

H.  Hantzsch  und  B.  Issaias,  Uber  polychrome  und 
chromotrope  Violurate.  Ber.  42,  1000.  Centr.  B.  1909,  I,  1395. 

R.  Behrend  und  R.  Schultz,  Uber  die  Oxydation  des  Harn- 
saure  in  alkalischer  Losung.  Ann.  365,  21.  Centr.  B.  1909, 

I,  1378. 

O.  Kiihling  und  B.  Schneider,  Uber  Kondensationspro- 
dukte  des  Alloxans.  Ber.  42,  1285.  Centr.  B.  1909,  I,  1548, 
1952. 

F.  G.  Dunan  and  W.  Schneider,  The  Colour  of  Aqueous 
Solutions  of  Violuric  Acid.  Jour.  Chem.  Soc.  (London),  95, 
956.  Centr.  B.  1909,  II,  348. 

J.  K.  Wood  and  E.  A.  Anderson,  The  Constitution  of  the 
Salts  of  Barbituric  Acid.  Jour.  Chem.  Soc.  (London),  95, 
979.  Centr.  B.  1909,  II,  426. 

T.  B.  Johnson  and  D.  B.  Jones,  Synthesis  of  1-Methyl- 
5-oxyuracil.  Jour.  Amer.  Chem.  Soc.  31,  590.  Centr.  B.  1909, 

II,  545. 

J.  Posner  und  K.  Rohde,  Beitrage  zur  Kenntniss  der 
ungesattigten  Verbindungen.  Uber  die  Addition  von  Hy- 
droxylamin  auf  ungesattigte  Sauren  mit  Konjugierten  Doppel- 
bindungen.  Ber.  42,  2785.  Centr.  B.  1909,  II,  705.  (Cin- 
namenyldihydrouracil) . 

H.  L.  Wheeler  and  T.  B.  Johnson,  The  Preparation  of 
3-Methyl  and  3-Benzyluracil.  Amer.  Chem.  Jour.  42,  30. 
Centr.  B.  1909,  II,  1047. 

H.  L.  Wheeler  and  D.  F.  McFarland.  The  Preparation  of 
1,  4-Dimethyluracil  and  the  Monobenzyl  Derivatives  of  4- 
Methyluracil.  Amer.  Chem.  Jour.  42,  101.  Centr.  B.  1909,  II, 
1048. 

T.  B.  Johnson  and  H.  H.  Guest,  Sulphur  Derivatives  of 
5-Oxyuracil.  Pheparation  of  5-Benzylmercaptouracil  and  5- 
Benzylmercaptocytosine.  Amer.  Chem.  Jour.  42,  271.  Centr. 
B.  1909,  II,  1637. 

T.  B.  Johnson  and  K.  G.  Mackenzie,  Dimethyl  Derivatives 
of  2-Aminopyrimidine.  Preparation  of  2-Methylamino-5- 
Methylpyrimidine.  Amer.  Chem.  Jour.  42,  353.  Centr.  B. 
1910,  I,  284. 

H.  L.  Wheeler  and  D.  F.  McFarland,  The  Action  of 
Methyl  Iodide  and  of  Benzyl  Chloride  Upon  2-Oxy-4-Methyl- 
6-Methylmercaptopyrimidine.  Amer.  Chem.  Jour.  42,  431. 
Centr.  B.  1910,  I,  1030. 

T.  B.  Johnson,  Synthesis  of  5-Cyanuracil.  Amer.  Chem. 
Jour.  42,  505. 

H.  L.  Wheeler  and  D.  F.  McFarland,  The  Thio  Deriva- 


24  BIBLIOGRAPHY 

tives  of  Thymine  and  the  Preparation  of  Thymine.  Amer. 
Chem.  Jour.  43,  19. 

C.  Billow  und  K.  Haas,  Synthetische  Versuche  zur  Dar- 
stellung  von  Derivaten  des  heterokondensierten  heterocyclis- 
chen  1,  3-Triazo-7,  0-pyrimidins.  Ber.  42,  4638.  Centr.  B. 
1910,  I,  286. 

J.  Zerewitinow,  Uber  die  organischen  Salze  der  Violur- 
saure.  Ber.  42,  4802.  Centr.  B.  1910,  I,  342. 


PATENTS 

1900. 
Centr.  B.     1.     113. 

1901. 
Centr.  B.  I.  547,  1219. 

1902. 
Centr.  B.  II.  1165,  1229. 

1903. 
Centr.  B.  II.  778,  813,  1483. 

1904. 

Centr.  B.  I.  68,  69,  619. 
II.  1631. 

1905. 

Centr.  B.  1.   54,  58,  636,  784,  841. 
II.  182,  728,  798,  1141,  1756. 

1906. 
Centr.  B.  1.  300,  370,  514,  618,  620. 

881,  1199,  1200,  1383,  1809,  1810. 
Centr.  B.  II.   386,  574,  725,  835,  984,  1093,  1371. 

1465,  1696,  1792. 

1907. 
Centr.  B.  I.  198,  774,  1295,  1648. 

II.  198,  276,  655,  956,  2001. 

1908. 
Centr.  B.  I.  919. 

1909. 

Centr.  B.  I.   233,  1283. 
II.  1182. 


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